U.S. patent application number 12/670721 was filed with the patent office on 2010-08-05 for support for separation membrane, and method for production thereof.
This patent application is currently assigned to TORAY INDUSTRIES, INC.. Invention is credited to Ryoichi Hane, Tatsuya Kajino, Hiroyuki Matsuura, Yohei Nakano, Jun Ogihara, Naoki Shibusawa, Yoshikazu Yakake.
Application Number | 20100193428 12/670721 |
Document ID | / |
Family ID | 40304316 |
Filed Date | 2010-08-05 |
United States Patent
Application |
20100193428 |
Kind Code |
A1 |
Hane; Ryoichi ; et
al. |
August 5, 2010 |
SUPPORT FOR SEPARATION MEMBRANE, AND METHOD FOR PRODUCTION
THEREOF
Abstract
A support for a separation membrane includes a long-fiber
nonwoven fabric composed of thermoplastic continuous filaments.
Inventors: |
Hane; Ryoichi; (Shiga,
JP) ; Ogihara; Jun; (Ehime, JP) ; Matsuura;
Hiroyuki; (Shiga, JP) ; Nakano; Yohei; (Shiga,
JP) ; Shibusawa; Naoki; (Shiga, JP) ; Kajino;
Tatsuya; (Shiga, JP) ; Yakake; Yoshikazu;
(Shiga, JP) |
Correspondence
Address: |
IP GROUP OF DLA PIPER LLP (US)
ONE LIBERTY PLACE, 1650 MARKET ST, SUITE 4900
PHILADELPHIA
PA
19103
US
|
Assignee: |
TORAY INDUSTRIES, INC.
Tokyo
JP
|
Family ID: |
40304316 |
Appl. No.: |
12/670721 |
Filed: |
July 28, 2008 |
PCT Filed: |
July 28, 2008 |
PCT NO: |
PCT/JP2008/063506 |
371 Date: |
January 26, 2010 |
Current U.S.
Class: |
210/489 ;
156/288; 156/324; 442/327; 442/382; 442/392; 442/401 |
Current CPC
Class: |
B32B 2307/538 20130101;
B32B 5/26 20130101; B32B 2307/54 20130101; Y10T 442/681 20150401;
B32B 2262/0276 20130101; B32B 2262/12 20130101; B32B 2307/72
20130101; B32B 2307/40 20130101; B32B 2307/50 20130101; B32B 5/08
20130101; Y10T 442/66 20150401; Y10T 442/671 20150401; B01D 69/10
20130101; D04H 3/16 20130101; B32B 2307/718 20130101; B01D 71/68
20130101; B32B 2307/734 20130101; Y10T 442/60 20150401; B32B 5/22
20130101; B32B 2307/724 20130101; B32B 2250/20 20130101; B32B 5/022
20130101 |
Class at
Publication: |
210/489 ;
442/327; 442/392; 442/382; 442/401; 156/324; 156/288 |
International
Class: |
B01D 69/10 20060101
B01D069/10; D04H 13/00 20060101 D04H013/00; B32B 5/26 20060101
B32B005/26; B01D 67/00 20060101 B01D067/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 31, 2007 |
JP |
2007-198581 |
Sep 25, 2007 |
JP |
2007-246738 |
Oct 30, 2007 |
JP |
2007-281308 |
Claims
1. A support for a separation membrane comprising a long-fiber
nonwoven fabric composed of thermoplastic continuous filaments.
2. The support for a separation membrane according to claim 1,
wherein the long-fiber nonwoven fabric is a laminated long-fiber
nonwoven fabric formed by laminating 2 to 5 sheets of nonwoven
fabrics made of long fibers.
3. The support for a separation membrane according to claim 2,
wherein at least one layer in the laminated long-fiber nonwoven
fabric is a spunbonded nonwoven fabric.
4. The support for a separation membrane according to claim 1,
wherein the long-fiber nonwoven fabric substantially comprises only
spunbonded nonwoven fabric(s).
5. The support for a separation membrane according to claim 1
wherein tensile strength in a crosswise direction of the long-fiber
nonwoven fabric is 50 N/5 cm or more and a ratio of tensile
strength in a machine direction to tensile strength in a crosswise
direction is 2.7 or less.
6. The support for a separation membrane according to claim 1,
wherein tensile strength of the long-fiber nonwoven fabric is 80 to
900 N/5 cm, tensile elongation of the long-fiber nonwoven fabric is
15 to 50%, and a product of tensile strength and tensile elongation
calculated by the following equation: Product of tensile strength
and tensile elongation[N/5 cm]=tensile strength[N/5
cm].times.(1+tensile elongation[%]/100), is 120 to 1300 N/5 cm.
7. The support for a separation membrane according to claim 1,
wherein both stresses of elongation of 5% in a machine direction
and a crosswise direction of the long-fiber nonwoven fabric are 50
N/5 cm or more.
8. The support for a separation membrane according to claim 1,
wherein a ratio of stress of elongation of 5% in a lengthwise
direction to stress of elongation of 5% in a crosswise direction of
the long-fiber nonwoven fabric is 2.7 or less.
9. The support for a separation membrane according to claim 1,
wherein the thermoplastic continuous filament is a complex-type
filament made of polymers having different melting points, in which
a low melting point polymer having a melting point lower by 10 to
140.degree. C. than that of a high melting point polymer is
arranged about the high melting point polymer.
10. The support for a separation membrane according to claim 1,
wherein a coefficient of variance of luminance of transmitted light
of the long-fiber nonwoven fabric is 1.0 to 6.0%.
11. The support for a separation membrane according to claim 1,
wherein a packed density of the long-fiber nonwoven fabric is 0.4
to 0.8, an air permeability is 0.2 to 30.0 cc/cm.sup.2/sec, and a
change rate between a thickness at a low load (an indenter of 16 mm
in diameter, load 2 kPa) and a thickness at a high load (an
indenter of 16 mm in diameter, load 200 kPa) is 0.00 to 0.03
mm.
12. The support for a separation membrane according to claim 1,
wherein average surface roughness of the long-fiber nonwoven fabric
is 2 to 9 .mu.m.
13. A separation membrane produced by forming a membrane having a
separation function on the surface of the support for a separation
membrane according to claim 1.
14. A fluid separation element including the separation membrane
according to claim 13 as a constituent.
15. A method for producing a support for a separation membrane
comprising: thermocompression bonding long-fiber nonwoven fabrics
composed of thermoplastic continuous filaments or a laminated body
thereof between a pair of upper/lower flat rolls; and maintaining
at least one of the rolls at a temperature lower by 80 to
20.degree. C. than a melting point of a polymer composing at least
the surface of the thermoplastic continuous filament, to unify
them.
16. The method according to claim 15, in which a temperature
difference is made between flat rolls by setting a temperature of
flat roll on a high-temperature side at a temperature lower by 80
to 20.degree. C. than a melting point of a polymer composing the
surface of the thermoplastic continuous filament and setting a
temperature of flat roll on a low-temperature side at a temperature
lower by 40 to 120.degree. C. than a temperature of the flat roll
on a high-temperature side and thermocompression bonding is
performed.
17. The method according to claim 15 in which long-fiber nonwoven
fabrics composed of thermoplastic continuous filaments are
preliminarily thermocompression bonded between a pair of
upper/lower flat rolls, or between one flat roll and a collecting
conveyor used for collecting fibrous web at a temperature lower by
120 to 20.degree. C. than a melting point of a polymer composing at
least the surface of the thermoplastic continuous filament, and
plural sheets of the nonwoven fabric preliminarily
thermocompression bonded are superimposed on one another, and the
resulting laminated body is thermocompression bonded between a pair
of upper/lower flat rolls, at least one of which is maintained at a
temperature lower by 80 to 20.degree. C. than a melting point of a
polymer composing at least the surface of the thermoplastic
continuous filament, and unified.
18. The method according to claim 15, wherein the pair of flat
rolls are metallic for both an upper roll and a lower roll.
19. The method according to claim 15, wherein one of the pair of
flat rolls is a metal roll and the other is an elastic roll.
Description
RELATED APPLICATIONS
[0001] This is a .sctn.371 of International Application No.
PCT/JP2008/063506, with an international filing date of Jul. 28,
2008 (WO 2009/017086 A1, published Feb. 5, 2009), which is based on
Japanese Patent Application Nos. 2007-198581, filed Jul. 31, 2007,
2007-246738, filed Sep. 25, 2007, and 2007-281308, filed Oct. 30,
2007, the subject matter of which is incorporated by reference.
TECHNICAL FIELD
[0002] This disclosure relates to a support for a separation
membrane, which comprises a long-fiber nonwoven fabric composed of
thermoplastic continuous filaments and is used for supporting a
separation membrane such as a microfiltration membrane, an
ultrafiltration membrane, a nanofiltration membrane and a reverse
osmotic membrane, and a method for producing the same. Further, the
disclosure relates to a separation membrane using the support for a
separation membrane, and a fluid separation element.
BACKGROUND
[0003] In water treatment in recent years, membrane technology is
applied to many cases. For example, water treatment in a water
treatment plant, microfiltration membranes and ultrafiltration
membranes are used, and reverse osmosis membranes are used for
seawater desalination. Further, water for semiconductor production,
boiler feed water, water for medical service and pure water for
laboratory, reverse osmosis membranes and nanofiltration membranes
are used. Furthermore, to sewage water/waste water treatment, a
membrane-separation activated sludge method using microfiltration
membranes and ultrafiltration membranes is applied.
[0004] These separation membranes are broadly divided into a plain
membrane and a hollow-fiber membrane. Among these membrane, the
plain membrane mainly formed from synthesized polymers is often
used generally in combination with a support such as a nonwoven
fabric or a web since it is inferior in mechanical strength by a
membrane having a separation function alone.
[0005] Generally, a membrane having a separation function and a
support are unified by a method of fixing the membrane and the
support to each other by applying a polymer solution, which is a
raw material of the membrane having a separation function, onto the
support such as a nonwoven fabric, a fabric or the like and
spreading the polymer solution. Further, in a semi-permeable
membrane such as a reverse osmosis membrane or the like, the
membrane and the support are unified by a method in which a
supporting layer is formed by applying a polymer solution onto the
support such as a nonwoven fabric, a fabric or the like and
spreading the polymer solution, and then a semipermeable membrane
is formed on the supporting layer.
[0006] Therefore, the nonwoven fabric, the fabric and the like to
become a support require such an excellent film-forming property
that when applying and spreading a polymer solution, the polymer
solution does not cause strike through due to excessive permeation,
membrane substances do not peel and defects such as nonuniform
membranes and pinholes due to fuzz of the support are not
produced.
[0007] Further, in the case of a semipermeable membrane such as a
reverse osmosis membrane often used under a high pressure,
particularly, the support requires high mechanical strength and
high dimensional stability.
[0008] Hitherto, as such a support for a separation membrane, a
support for a separation membrane comprising a nonwoven fabric
having a multilayered structure, in which a two-layered structure
including a surface layer having large opening and surface
roughness using thick fibers and a backside layer having small
opening and a compact structure using thin fibers is basic, is
proposed (Japanese Examined Patent Publication No. 4-21526).
Further, in a support for a semipermeable membrane comprising a
nonwoven fabric for applying and spreading a polymer solution for
forming a semipermeable membrane to form a membrane, a support for
a semipermeable membrane, in which the nonwoven fabric is a
nonwoven fabric having a two-layered structure formed by laminating
and unifying a low-density layer where air permeability is 5 to 50
cc/cm.sup.2/sec and a high-density layer where air permeability is
0.1 cc/cm.sup.2/sec or more and less than 5 cc/cm.sup.2/sec, and
overall air permeability is 0.1 cc/cm.sup.2/sec to 4.5
cc/cm.sup.2/sec, is proposed (Japanese Examined Patent Publication
No. 5-35009).
[0009] However, since these supports for membrane comprise composed
of short fibers instead of a continuous fiber, a nonuniform
membranes and defects may be produced due to fuzz. Furthermore, in
these documents, there is no proposal about strength of the
nonwoven fabric, and since there is not detail description about
strength, there is a problem that adequate mechanical strength and
dimensional stability cannot be achieved as a support for a
membrane.
[0010] Further, aside from these supports for a separation
membrane, as such a support for a separation membrane, a support
for a semipermeable membrane comprising a nonwoven fabric in which
an average of a breaking length of elongation of 5% in a machine
direction (MD) and a breaking length of elongation of 5% in a
crosswise direction (CD) is 4.0 km or more and air permeability is
0.2 to 10.0 cc/cm.sup.2sec is proposed (Japanese Patent Publication
No. 3153487). However, this support for a semipermeable membrane is
not composed of continuous filaments, but comprises a nonwoven
fabric composed of short fibers produced by a papermaking method.
Therefore, to obtain a semipermeable membrane having required high
mechanical strength, this requires many complicated steps, for
example, yarn is stretched in warm water bath after melt spinning,
and subsequently double refraction of fiber composing a nonwoven
fabric is significantly increased by stretched heat treatment
and/or relaxed heat treatment, and heat shrinkage stress is set at
a specified range. Accordingly, the support for a semipermeable
membrane of this proposal has problems that the support becomes
expensive, and since it comprises a nonwoven fabric composed of
short fibers, a nonuniform membranes and defects may be produced
due to fuzz.
[0011] Therefore, it could be helpful to provide a support for a
separation membrane, which comprises a long-fiber nonwoven fabric
composed of thermoplastic continuous filaments and exhibits an
excellent film-forming property and excellent mechanical strength
when used for supporting a separation membrane such as a
microfiltration membrane, an ultrafiltration membrane, a
nanofiltration membrane and a reverse osmotic membrane, and a
method for producing the same.
[0012] It could also be helpful to provide a separation membrane
and a fluid separation element each utilizing the support for a
separation membrane.
SUMMARY
[0013] We provide a support for a separation membrane comprising a
long-fiber nonwoven fabric composed of thermoplastic continuous
filaments.
[0014] In accordance with a preferable aspect of the support for a
separation membrane, the long-fiber nonwoven fabric is a laminated
long-fiber nonwoven fabric formed by laminating 2 to 5 sheets of
nonwoven fabrics made of long fibers.
[0015] In accordance with a preferable aspect of the support for a
separation membrane, at least one layer in the laminated long-fiber
nonwoven fabric is a spunbonded nonwoven fabric.
[0016] In accordance with a preferable aspect of the support for a
separation membrane, the long-fiber nonwoven fabric substantially
comprises only spunbonded nonwoven fabric(s).
[0017] In accordance with a preferable aspect of the support for a
separation membrane, tensile strength in a crosswise direction of
the long-fiber nonwoven fabric is 50 N/5 cm or more and a ratio of
tensile strength in a machine direction to tensile strength in a
crosswise direction is 2.7 or less.
[0018] In accordance with a preferable aspect of the support for a
separation membrane, tensile strength of the long-fiber nonwoven
fabric is 80 to 900 N/5 cm, tensile elongation of the long-fiber
nonwoven fabric is 15 to 50%, and a product of tensile strength and
tensile elongation calculated by the following equation:
Product of tensile strength and tensile elongation[N/5 cm]=tensile
strength[N/5 cm].times.(1+tensile elongation[%]/100),
is 120 to 1300 N/5 cm.
[0019] In accordance with a preferable aspect of the support for a
separation membrane, both stresses of elongation of 5% in a machine
direction and a crosswise direction of the long-fiber nonwoven
fabric are 50 N/5 cm or more.
[0020] In accordance with a preferable aspect of the support for a
separation membrane, a ratio of stress of elongation of 5% in a
machine direction to stress of elongation of 5% in a crosswise
direction of the long-fiber nonwoven fabric is 2.7 or less.
[0021] In accordance with a preferable aspect of the support for a
separation membrane, the thermoplastic continuous filament is a
complex-type filament made of polymers having different melting
points, in which a low melting point polymer having a melting point
lower by 10 to 140.degree. C. than that of a high melting point
polymer is arranged about the high melting point polymer.
[0022] In accordance with a preferable aspect of the support for a
separation membrane, a coefficient of variance of luminance of
transmitted light of the long-fiber nonwoven fabric is 1.0 to
6.0%.
[0023] In accordance with a preferable aspect of the support for a
separation membrane, a packed density of the long-fiber nonwoven
fabric is 0.4 to 0.8, an air permeability is 0.2 to 30.0
cc/cm.sup.2/sec, and a change rate between a thickness at a low
load (an indenter of 16 mm in diameter, load 2 kPa) and a thickness
at a high load (an indenter of 16 mm in diameter, load 200 kPa) is
0.00 to 0.03 mm.
[0024] In accordance with a preferable aspect of the support for a
separation membrane, average surface roughness of the long-fiber
nonwoven fabric is 2 to 9
[0025] A separation membrane can be obtained by forming a membrane
having a separation function on the surface of the support for a
separation membrane. Further, a fluid separation element including
the separation membrane as a constituent can be obtained.
[0026] Further, we provide a method for producing a support for a
separation membrane comprising the step of thermocompression
bonding long-fiber nonwoven fabrics composed of thermoplastic
continuous filaments or a laminated body thereof between a pair of
upper/lower flat rolls, at least one of which is maintained at a
temperature lower by 80 to 20.degree. C. than a melting point of a
polymer composing at least the surface of the thermoplastic
continuous filament, to unify them.
[0027] Further, in accordance with a preferable aspect of the
method for producing a support for a separation membrane, a
temperature difference is made between flat rolls by setting a
temperature of flat roll on a high-temperature side at a
temperature lower by 80 to 20.degree. C. than a melting point of a
polymer composing the surface of the thermoplastic continuous
filament and setting a temperature of flat roll on a
low-temperature side at a temperature lower by 40 to 120.degree. C.
than a temperature of the flat roll on a high-temperature side, and
thermocompression bonding is performed.
[0028] Further, the method for producing a support for a separation
membrane is a method in which long-fiber nonwoven fabrics composed
of thermoplastic continuous filaments are preliminarily
thermocompression bonded between a pair of upper/lower flat rolls,
or between one flat roll and a collecting conveyor used for
collecting fibrous web at a temperature lower by 120 to 20.degree.
C. than a melting point of a polymer composing at least the surface
of the thermoplastic continuous filament, and plural sheets of the
nonwoven fabric preliminarily thermocompression bonded are
superimposed on one another, and the resulting laminated body is
thermocompression bonded between a pair of upper/lower flat rolls,
at least one of which is maintained at a temperature lower by 80 to
20.degree. C. than a melting point of a polymer composing at least
the surface of the thermoplastic continuous filament, and
unified.
[0029] In accordance with a preferable aspect of the
above-mentioned method for producing a support for a separation
membrane, the above-mentioned pair of flat rolls are metallic for
both an upper roll and a lower roll.
[0030] In accordance with a preferable aspect of the
above-mentioned method for producing a support for a separation
membrane, one of the above-mentioned pair of flat rolls is a metal
roll and the other is an elastic roll.
[0031] We obtain a support for a separation membrane, which
comprises a long-fiber nonwoven fabric composed of thermoplastic
continuous filaments and exhibits an excellent film-forming
property and excellent mechanical strength when used for supporting
a separation membrane such as a microfiltration membrane, an
ultrafiltration membrane, a nanofiltration membrane and a reverse
osmotic membrane.
[0032] Further, we obtain a support for a separation membrane
comprising a long-fiber nonwoven fabric which is composed of
thermoplastic continuous filaments and is superior in uniformity of
weight per unit area in a minute area.
[0033] Further, we obtain a support for a separation membrane in
which the depression into an indentation of a material of a
permeated liquid flow passage is less even when a high reverse
osmotic pressure is applied and permeated liquid can stably passes
through and therefore high water re-use capacity can be secured
since a long-fiber nonwoven fabric, which is composed of
thermoplastic continuous filaments and has a small difference
between strength in a machine direction and strength in a crosswise
direction, is used.
[0034] Furthermore, we obtain a support for a separation membrane
which can suppress distortion due to bending in a lateral direction
or tension of a process step when forming a membrane to form a
membrane uniformly.
DETAILED DESCRIPTION
[0035] A support for a separation membrane is a support for a
separation membrane for forming a membrane having a separation
function on the surface thereof.
[0036] It is important that a support for a separation membrane
comprises a long-fiber nonwoven fabric composed of thermoplastic
continuous filaments. We investigated the causes of nonuniformity
of a polymer solution in applying and spreading the polymer
solution and membrane defects, which often occur in the case of
using a nonwoven fabric composed of short fibers, and found that
the fuzz of fibers composing the nonwoven fabric composed of short
fibers contribute to these problems. Further, we found that these
problems can be solved by using a nonwoven fabric composed of long
fibers. That is, by using a long-fiber nonwoven fabric composed of
thermoplastic continuous filaments, it is possible to suppress
nonuniformity of a polymer solution in applying and spreading the
polymer solution and membrane defects, which are produced due to
the fuzz of fibers occurring in the case of using a nonwoven fabric
composed of short fibers.
[0037] Moreover, since the support for a separation membrane is a
long-fiber nonwoven fabric composed of thermoplastic continuous
filaments, it has higher mechanical strength than a nonwoven fabric
composed of short fibers, especially a paper nonwoven fabric in
which a fiber length is short. Accordingly, the support for a
separation membrane exhibits excellent durability as a support for
a semipermeable membrane to which high pressure is particularly
applied during use among the supports for a separation
membrane.
[0038] A nonwoven fabric composing the support for a separation
membrane is a long-fiber nonwoven fabric composed of thermoplastic
continuous filaments such as a spunbonded non-woven fabric produced
by a spunbonding method, melt blowing nonwoven fabric produced by a
melt blowing method or the like. The long-fiber nonwoven fabric is
preferably a spunbonded nonwoven fabric because when forming a
separation membrane on the spunbonded nonwoven fabric, a separation
membrane having a good film-forming property and excellent
durability can be obtained and the obtained separation membrane is
more superior in mechanical strength and dimensional stability.
[0039] Further, the long-fiber nonwoven fabric composing the
support for a separation membrane may be a monolayer, but a
laminated body (referred to as a laminated long-fiber nonwoven
fabric) consisting of a plurality of long-fiber nonwoven fabrics is
also a preferable form since by the laminated body, a more uniform
support for a separation membrane can be obtained as described
later. The laminated long-fiber nonwoven fabric preferably
comprises a laminated body in which at least one layer in the
laminated body is a spunbonded nonwoven fabric, for example, a
three-layered laminated body in which a sheet of melt blowing
nonwoven fabric is disposed between layers of a two-layered
spunbonded nonwoven fabric. Further, an aspect, in which the
laminated long-fiber nonwoven fabric substantially comprises only
spunbonded nonwoven fabric(s) like a laminated body composed of a
two-layered spunbonded non-woven fabric, is preferable.
[0040] The thermoplastic continuous filaments composing the
long-fiber nonwoven fabric may be thermoplastic continuous
filaments made of a single component, or may be complex-type
thermoplastic continuous filaments made of a plurality of
components. In the support for a separation membrane, a preferable
aspect is that the support for a separation membrane comprises a
long-fiber nonwoven fabric composed of the complex-type
thermoplastic continuous filaments (referred to as complex-type
filaments) in which two or more polymers having different melting
points are used and a low melting point polymer having a melting
point lower by 10 to 140.degree. C. than that of a high melting
point polymer is arranged about the high melting point polymer.
[0041] By arranging the low melting point polymer having a melting
point lower by 10 to 140.degree. C. than that of a high melting
point polymer about the high melting point polymer, complex-type
filaments composing the long-fiber nonwoven fabric are firmly
bonded to one another when a long-fiber nonwoven fabric is formed
by thermocompression bonding and the formed long-fiber nonwoven
fabric is used as a support for a separation membrane. Accordingly,
it is possible to suppress nonuniformity of a polymer solution in
applying and spreading the polymer solution and membrane defects
due to the fuzz of fibers. Further, by using such a complex-type
filament, number of bonded points increases compared with a mixed
type nonwoven fabric in which plural species of fibers having
different melting points are mixed in addition to the fact that
complex-type filaments composing the long-fiber nonwoven fabric are
firmly bonded to one another. Therefore, use of the complex-type
filament leads to improvements in dimensional stability and
durability in using as a support for a semipermeable membrane to
which among others, a high pressure is applied in use.
[0042] In a complex-type filament, if a difference in melting point
between the high melting point polymer and the low melting point
polymer is 10.degree. C. or more, desired thermobonding can be
achieved. Further, when the melting point difference is 140.degree.
C. or less, it is possible to prevent a low melting point polymer
component from fusing with a thermocompression bonding roll during
thermocompression bonding, leading to the reduction of
productivity. The melting point difference between the high melting
point polymer and the low melting point polymer is more preferably
in a range of 20 to 120.degree. C., and furthermore preferably in a
range of 30 to 100.degree. C.
[0043] Further, a melting point of the high melting point polymer
in the case where the support for a separation membrane comprises
the long-fiber nonwoven fabric composed of the complex-type
filaments is preferably in a range of 160 to 320.degree. C. because
when forming a separation membrane on the support for a separation
membrane, a separation membrane having a good film-forming property
and excellent durability can be obtained. When the melting point of
the high melting point polymer is 160.degree. C. or higher, in the
case where the long-fiber nonwoven fabric is formed and used as a
support for a separation membrane, form stability is high even when
the nonwoven fabric undergoes a process to which heat is added
during producing separation membranes or fluid separation elements.
Further, when a melting point of the high melting point polymer is
320.degree. C. or less, it is possible to prevent heat energy used
for melting during producing long-fiber nonwoven fabrics from being
consumed largely, leading to the reduction of productivity. The
melting point of the high melting point polymer is preferably in a
range of 170 to 300.degree. C., and more preferably in a range of
180 to 280.degree. C.
[0044] A percentage which the low melting point polymer makes up in
the complex-type filament is preferably 10 to 70% by weight from
the viewpoint of obtaining a long-fiber nonwoven fabric suitable
for a support for a separation membrane. The percentage of the low
melting point polymer is more preferably 15 to 60% by weight, and
furthermore preferably 20 to 50% by weight. When the percentage of
the low melting point polymer is 10% by weight or more, desired
thermobonding can be achieved. Further, when the percentage is 70%
by weight or less, it is possible to prevent a low melting point
polymer component from fusing with a thermocompression bonding roll
during thermocompression bonding, leading to the reduction of
productivity.
[0045] Examples of complex forms of the complex-type filaments
include forms such as a concentric core-sheath type, an eccentric
core-sheath type and a sea-island type from the viewpoint of
obtaining a long-fiber nonwoven fabric suitable for a support for a
separation membrane. Furthermore, examples of the shape of a cross
section of the complex-type filament include a circular cross
section, a planiform cross section, a polygonal cross section, a
multifoil cross section, and a hollow cross section. Among these
forms, a concentric filament of a core-sheath type is preferably
used as a complex form and a circular cross section or a planiform
cross section is preferably used as a shape of a cross section of
the filament because these filaments can be firmly bonded to one
another by thermocompression bonding and a thickness of the
resulting support for a separation membrane can be reduced to
increase an area of the separation membrane per a unit of a fluid
separation element.
[0046] It is a preferable form of the long-fiber nonwoven fabric
composing the support for a separation membrane that it is a
laminated long-fiber nonwoven fabric consisting of a plurality of
long-fiber nonwoven fabric layers as described above. By forming a
laminated body like this, it is possible to obtain a more uniform
support for a separation membrane, and by forming an interface
between laminated layers, it is possible to prevent strike through
due to excessive permeation in applying and spreading a polymer
solution and obtain an excellent film-forming property. Number of
laminated layers of the laminated long-fiber nonwoven fabric is
preferably 2 to 5. When the number of laminated layers is two or
more, a texture of the nonwoven fabric is improved and adequate
uniformity is attained compared with the case of monolayer. When
the number of laminated layers is five or less, wrinkles produced
during lamination can be suppressed and delamination can be
inhibited.
[0047] Examples of methods of unifying the laminated long-fiber
nonwoven fabric include compression bonding by heat, compression
bonding using an adhesive, and mechanical entanglement and further
combinations thereof. Among these methods, compression bonding by
heat using a pair of flat rolls is a preferable means because a
thickness of the resulting support for a separation membrane can be
reduced to increase an area of the separation membrane per a unit
of a fluid separation element. Further, a combination of
compression bonding by heat and compression bonding using an
adhesive is also preferably employed. Examples of the adhesive
include powders, fibers, and nonwoven fabrics, which are made of a
resin having a melting point lower than a melting point of the
long-fiber nonwoven fabric to be laminated.
[0048] The support for a separation membrane preferably has high
rigidity and high toughness capable of standing a high pressure
particularly in the case of being used as a support for separation
membranes such as a reverse osmosis membrane and the like. Herein,
preferable rigidity refers to rigidity for avoiding distortions due
to a high reverse osmotic pressure. Further, the toughness is
toughness for avoiding breakage due to momentarily applied forces
such as pressure fluctuation. We noted a balance between the
tensile strength and the tensile elongation of the long-fiber
nonwoven fabric composing the support for a separation membrane to
achieve both characteristics of rigidity and toughness. We found
that both rigidity and toughness of a support for a separation
membrane are improved by enhancing both of the tensile strength and
the tensile elongation of the support for a separation membrane,
that is, enhancing a product of the tensile strength and the
tensile elongation, since the rigidity and the toughness suitable
as the support for a separation membrane are not improved even when
only one of the tensile strength and the tensile elongation is
enhanced. Herein, the product of tensile strength and tensile
elongation is a value calculated by the following equation:
Product of tensile strength and tensile elongation[N/5 cm]=tensile
strength[N/5 cm].times.(1+tensile elongation[%]/100).
[0049] Next, the tensile strength, the tensile elongation and the
product of tensile strength and tensile elongation will be
described in detail.
[0050] The tensile strength of the long-fiber nonwoven fabric
composing the support for a separation membrane is preferably 80 to
900 N/5 cm. The tensile strength is more preferably 90 to 850 N/5
cm, and furthermore preferably 100 to 700 N/5 cm.
[0051] Further, the tensile elongation of the long-fiber nonwoven
fabric is preferably 15 to 50%. The tensile elongation is more
preferably 18 to 45%, and furthermore preferably 20 to 40%.
[0052] Furthermore, the product of tensile strength and tensile
elongation of the long-fiber nonwoven fabric is preferably 120 to
1300 N/5 cm, more preferably 170 to 1100 N/5 cm, and furthermore
preferably 220 to 900 N/5 cm.
[0053] When the tensile strength and the tensile elongation of the
support for a separation membrane along a direction perpendicular
to a direction of a groove made of a material of a permeated liquid
flow passage are high, rigidity for the stress on the separation
membrane, which is generated through the depression of the
separation membrane in the material of a permeated liquid flow
passage at the time of applying a pressure vertically to the
separation membrane, is improved. However, if the tensile strength
is too high, a feeling of the separation membrane becomes hard, and
toughness against a pressure in a vertical direction is
deteriorated. On the contrary, if the tensile elongation is too
large, a problem that the depression rate of the support for a
separation membrane in the material of a permeated liquid flow
passage increases and a residual strain remains arises. Therefore,
if considering a balance between the tensile strength and the
tensile elongation, it is preferable that as described above, the
tensile strength is 80 to 900 N/5 cm, the tensile elongation is 15
to 50%, and the product of tensile strength and tensile elongation
is 120 to 1300 N/5 cm. By having a balance between the tensile
strength and the tensile elongation like this, distortions and
damages due to a pressure applied in using the long-fiber nonwoven
fabric as a support for a separation membrane are less and the
depression rate of the separation membrane in the material of a
permeated liquid flow passage becomes small, and therefore membrane
performance or a processing capacity is easily retained.
[0054] The tensile strength and the tensile elongation of the
long-fiber nonwoven fabric can be measured by a method described in
paragraph (3) in Examples described later.
[0055] To obtain the long-fiber nonwoven fabric composing the
support for a separation membrane in which the tensile strength is
80 to 900 N/5 cm, the tensile elongation is 15 to 50%, and the
product of tensile strength and tensile elongation is 120 to 1300
N/5 cm, the following means are preferably employed: [0056] (a) A
long-fiber nonwoven fabric substantially comprising only spunbonded
nonwoven fabric(s) is used. [0057] (b) When the long-fiber nonwoven
fabric is a laminated body consisting of a plurality of nonwoven
fabric layers, a spunbonded nonwoven fabric is used for at least
one layer in the laminated body. [0058] (c) As the thermoplastic
continuous filaments composing the long-fiber nonwoven fabric, a
complex-type filament, in which a low melting point polymer having
a melting point lower by 10 to 140.degree. C. than that ea high
melting point polymer is arranged about the high melting point
polymer, is used. [0059] (d) A spunbonded nonwoven fabric produced
at a spinning speed of 4000 m/min or more is used. [0060] (e) A
laminated long-fiber nonwoven fabric fabricated by a method, in
which long-fiber nonwoven fabrics composed of thermoplastic
continuous filaments or a laminated body thereof are preliminarily
thermocompression bonded between a pair of upper/lower flat rolls,
at least one of which is maintained at a temperature lower by 120
to 20.degree. C. than a melting point of a polymer composing at
least the surface of the thermoplastic continuous filament, or
between one flat roll and a collecting conveyor used for collecting
fibrous web, and in a continuous step or after the nonwoven fabric
in a state of temporary bonding, in which a high-density layer is
formed on a surface side and/or a backside, is taken up, plural
sheets of the nonwoven fabric in a state of temporary bonding,
preliminarily thermocompression bonded, are superimposed on one
another, and the resulting laminated body is thermocompression
bonded with a pair of upper/lower flat rolls, at least one of which
is maintained at a temperature lower by 80 to 20.degree. C. than a
melting point of a polymer composing at least the surface of the
thermoplastic continuous filament, and unified, is employed.
[0061] As raw materials of the thermoplastic continuous filaments
composing the long-fiber nonwoven fabric, polymers, which can
provide a long-fiber nonwoven fabric suitable for the support for a
separation membrane, are used. Examples of such raw materials
include polyester polymers, polyamide polymers, polyolefin
polymers, and mixtures or copolymers thereof. The raw materials are
preferably polyester polymers since a support for a separation
membrane, which is more excellent in durability such as mechanical
strength, heat resistance, water resistance, chemical resistance
and the like, can be obtained from the polyester polymers.
[0062] The polyester polymers are polyesters comprising an acid
component and an alcohol component. As acid components, aromatic
carboxylic acids such as terephthalic acid, isophthalic acid and
phthalic acid; aliphatic dicarboxylic acids such as adipic acid and
sebacic acid; and alicyclic dicarboxylic acids such as
cyclohexanecarboxylic acid can be used. Further, as alcohol
components, ethylene glycol, diethylene glycol and polyethylene
glycol can be used.
[0063] Examples of the polyester polymers include a polyethylene
terephthalate resin, a polybutylene terephthalate resin, a
polytrimethylene terephthalate resin, a polyethylene naphthalate
resin, a poly(lactic acid) resin and a poly(butylene succinate)
resin, and include copolymers of these resins.
[0064] Further, as described above, the complex-type filament made
of polymers having different melting points, in which a low melting
point polymer having a melting point lower by 10 to 140.degree. C.
than that of a high melting point polymer is arranged about the
high melting point polymer, can be used. Examples of a combination
(high melting point polymer/low melting point polymer) of the high
melting point polymer and the low melting point polymer in the case
of forming such the complex-type filament include polyethylene
terephthalate resin/polybutylene terephthalate resin, polyethylene
terephthalate resin/polytrimethylene terephthalate resin,
polyethylene terephthalate resin/poly(lactic acid) resin, and
polyethylene terephthalate resin/copolymerization polyethylene
terephthalate resin. Further, as a copolymerization component of a
copolymerization polyethylene terephthalate resin, isophthalic acid
and the like are preferably used.
[0065] Furthermore, biodegradable resins are preferably used as a
raw material of the thermoplastic continuous filament since
disposal is easy and an environmental burden is small in discarding
used supports for a separation membrane. Examples of the
biodegradable resins include a poly(lactic acid) resin, a
poly(butylene succinate) resin, a polycaprolactone resin, a
poly(ethylene succinate) resin, a poly(glycolic acid) resin, and a
poly(hydroxy butylate) resin. Among these resins, the poly(lactic
acid) resin derived from a lactic acid obtained by fermentation of,
which is a plant-derived resin not depleting petroleum resources
and attracts lots of attention in recent years as a biodegradable
resin of low production cost, having relatively high mechanical
characteristics and heat resistance, is preferably used as a raw
material of fibers composing a long-fiber nonwoven fabric. Examples
of the poly(lactic acid) resins preferably include poly(D-lactic
acid), poly(L-lactic acid), copolymers of D-lactic acid and
L-lactic acid, and blended substances thereof.
[0066] A crystal nucleus agent, a flatting agent, a lubricant, a
pigment, a fungicide, an anti-fungus agent, a retarder, and a
hydrophilization agent may be mixed in or added to the long-fiber
nonwoven fabric composing the support for a separation membrane to
the extent of not impairing an effect of this disclosure.
Particularly, metal oxides such as titanium oxide and the like has
an effect of improving a bonding property of the long-fiber
nonwoven fabric through enhancing thermal conductivity in molding
the long-fiber nonwoven fabric by thermocompression bonding.
Further, aliphatic bisamides such as ethylenebis(stearamide) and
the like and/or alkyl-substituted aliphatic monoamides has an
effect of improving bonding stability through enhancing a releasing
property of a long-fiber nonwoven fabric from a thermocompression
bonding roll. These various additives may be contained within the
thermoplastic continuous filament or may be present on the surface
thereof.
[0067] The support for a separation membrane preferably comprises
the long-fiber non-woven fabric in which a coefficient of variance
of luminance of transmitted light is 1.0 to 6.0%. The coefficient
of variance of luminance of transmitted light of the long-fiber
nonwoven fabric is more preferably 1.0 to 5.0%, and furthermore
preferably 1.0 to 4.0%. If the coefficient of variance of luminance
of transmitted light of the long-fiber nonwoven fabric is 1.0% or
more, when forming a separation membrane on the support for a
separation membrane, peeling of a membrane due to insufficient
permeation in applying and spreading a polymer solution is less and
a good film-forming property can be attained. On the other hand, if
the coefficient of variance of luminance of transmitted light of
the long-fiber nonwoven fabric is 6.0% or less, when using the
long-fiber nonwoven fabric as a support for a separation membrane,
the weight per unit area of a minute area is uniform. Therefore,
excessive permeation in applying and spreading a polymer solution
is suppressed and thereby strike through becomes less, and
therefore the long-fiber nonwoven fabric can be suitably used as a
support for a separation membrane.
[0068] The coefficient of variance of luminance of transmitted
light of the long-fiber nonwoven fabric refers to a coefficient of
variance determined from a standard deviation of luminance in
quantifying an amount of fiber in a minute area in terms of the
luminance of transmitted light in the minute area, and the
coefficient of variance refers to a value measured by a method
described in paragraph (5) in Examples described later.
[0069] To obtain the long-fiber nonwoven fabric composing the
support for a separation membrane in which the coefficient of
variance of luminance of transmitted light is 1.0 to 6.0%, it is
preferable to make a laminated nonwoven fabric formed by
laminating/unifying as a long-fiber nonwoven fabric. Number of
laminated layers of the long-fiber nonwoven fabric is preferably 2
to 5. When the number of laminated layers is two or more, a texture
of the nonwoven fabric is improved and adequate uniformity is
attained compared with the case of monolayer. When the number of
laminated layers is five or less, wrinkles produced during
lamination can be suppressed and delamination can be inhibited.
[0070] Further, to obtain the long-fiber nonwoven fabric composing
the support for a separation membrane in which the coefficient of
variance of luminance of transmitted light is 1.0 to 6.0%, it is
also preferable to set an average fiber diameter of thermoplastic
continuous filaments composing the long-fiber nonwoven fabric at 3
to 17 .mu.m. When an average fiber diameter of thermoplastic
continuous filaments is 3 .mu.m or more, since a spinning property
is hardly deteriorated during producing the long-fiber nonwoven
fabric and air permeability of the support for a separation
membrane can be maintained, peeling of a membrane in applying and
spreading a polymer solution is less and a good film-forming
property can be attained. On the other hand, when an average fiber
diameter of thermoplastic continuous filaments is 17 .mu.m or less,
since the long-fiber nonwoven fabric and the support for a
separation membrane, which are superior in uniformity, can be
attained and the support for a separation membrane can be more
dense, excessive permeation in applying and spreading a polymer
solution is less and an excellent film-forming property can be
attained.
[0071] In the long-fiber nonwoven fabric composing the support for
a separation membrane, it is preferable that tensile strength in a
crosswise direction is 50 to 900 N/5 cm and a ratio of tensile
strength in a machine direction to tensile strength in a crosswise
direction is 1.0 to 2.7. Further, an aspect, in which tensile
strength in a crosswise direction is 70 to 900 N/5 cm and a ratio
of tensile strength in a machine direction to tensile strength in a
crosswise direction is 1.0 to 2.5, is more preferable, and an
aspect, in which tensile strength in a crosswise direction is 90 to
900 N/5 cm and a ratio of tensile strength in a machine direction
to tensile strength in a crosswise direction is 1.0 to 2.3, is
furthermore preferable.
[0072] In the long-fiber nonwoven fabric, generally, the tensile
strength in a travelling direction or machine direction during
producing nonwoven fabrics has a tendency to become larger than the
tensile strength that in a crosswise direction. On the other hand,
since the separation membrane such as a reverse osmosis membrane is
often used in a state of being superimposed on another in such a
way that a direction of a groove of the material of a permeated
liquid flow passage is orthogonal to a crosswise direction of the
support for a separation membrane, if the tensile strength in a
crosswise direction of the long-fiber nonwoven fabric composing the
support for a separation membrane is 50 N/5 cm or more and a ratio
of tensile strength in a machine direction to tensile strength in a
crosswise direction is 2.7 or less, the separation membrane stands
a force whichever direction the force is applied to, and it is
possible to suppress the depression of the separation membrane into
a groove even when a particularly high reverse osmotic pressure is
applied to the separation membrane. On the other hand, if the
tensile strength in a crosswise direction is 900 N/cm or less, it
is possible to inhibit a change of a feeling to a hard feeling due
to a too high tensile strength, and if the ratio of tensile
strength in a machine direction to tensile strength in a crosswise
direction is 1.0 or more, it is possible to prevent the
productivity of the long-fiber nonwoven fabric from significantly
deteriorating.
[0073] The tensile strength in a crosswise direction and the ratio
of tensile strength in a machine direction to tensile strength in a
crosswise direction of the long-fiber nonwoven fabric refer to
values measured by a method described in paragraph (3) in Examples
described later.
[0074] To obtain the long-fiber nonwoven fabric composing the
support for a separation membrane in which tensile strength in a
crosswise direction is 50 to 900 N/5 cm and a ratio of tensile
strength in a machine direction to tensile strength in a crosswise
direction is 1.0 to 2.7, it is preferable to use the long-fiber
nonwoven fabric substantially comprising only spunbonded nonwoven
fabric(s) or to use a spunbonded nonwoven fabric for at least one
layer in a laminated body when the long-fiber nonwoven fabric is
the laminated body consisting of a plurality of non-woven fabric
layers. Further, an aspect of using a complex-type filament, in
which a low melting point polymer having a melting point lower by
10 to 140.degree. C. than that of a high melting point polymer is
arranged about the high melting point polymer, as a thermoplastic
continuous filament composing the long-fiber nonwoven fabric is
preferable for obtaining the long-fiber non-woven fabric in which
tensile strength in a crosswise direction is 50 to 900 N/5 cm and a
ratio of tensile strength in a machine direction to tensile
strength in a crosswise direction is 1.0 to 2.7.
[0075] A packed density of the long-fiber nonwoven fabric composing
the support for a separation membrane is preferably 0.4 to 0.8. The
packed density is more preferably 0.5 to 0.8, and furthermore
preferably 0.6 to 0.8. When the packed density is 0.4 or more,
since voids within the long-fiber nonwoven fabric are few, the
long-fiber nonwoven fabric is less prone to being distorted and
damaged by an external pressure when using it as a support for a
separation membrane. On the other hand, when the packed density is
0.8 or less, since water permeability or air permeability of the
long-fiber nonwoven fabric can be secured, pressure loss of a
support for a separation membrane does not become too high.
[0076] The packed density of the long-fiber nonwoven fabric refers
to a value measured by a method described in paragraph (8) in
Examples described later.
[0077] To obtain the long-fiber nonwoven fabric composing the
support for a separation membrane and having a packed density of
0.4 to 0.8, it is preferable to use a complex-type filament, in
which a low melting point polymer having a melting point lower by
10 to 140.degree. C. than that of a high melting point polymer is
arranged about the high melting point polymer, as a thermoplastic
continuous filament composing the long-fiber nonwoven fabric.
Further, an aspect, in which an average fiber diameter of
thermoplastic continuous filaments composing the long-fiber
nonwoven fabric is set at 3 to 17 .mu.m and a long-fiber nonwoven
fabric obtained by a spunbonding method is unified in the form of a
sheet by thermocompression bonding, is preferable for obtaining the
long-fiber nonwoven fabric having a packed density of 0.4 to
0.8.
[0078] An air permeability of the long-fiber nonwoven fabric
composing the support for a separation membrane is preferably 0.2
to 30.0 cc/cm.sup.2/sec. The air permeability is more preferably
0.3 to 20.0 cc/cm.sup.2/sec, and furthermore preferably 0.4 to 10.0
cc/cm.sup.2/sec. When the air permeability is 0.2 cc/cm.sup.2/sec
or more, pressure loss of a support for a separation membrane does
not become too high. On the other hand, when the air permeability
is 30.0 cc/cm.sup.2/sec or less, compactness of the long-fiber
nonwoven fabric can be maintained to facilitate formation of the
long-fiber nonwoven fabric.
[0079] The air permeability of the long-fiber nonwoven fabric
refers to a value measured by a method described in paragraph (9)
in Examples described later.
[0080] To obtain the long-fiber nonwoven fabric composing the
support for a separation membrane in which the air permeability is
0.2 to 30.0 cc/cm.sup.2/sec, an average fiber diameter of
thermoplastic continuous filaments composing the long-fiber
nonwoven fabric is preferably set at 3 to 17 .mu.m. Further, an
aspect, in which weight per unit area of the long-fiber nonwoven
fabric is 20 to 150 g/m.sup.2 and a long-fiber nonwoven fabric
obtained by a spunbonding method is unified in the form of a sheet
by thermocompression bonding, is preferable for obtaining the
long-fiber nonwoven fabric having an air permeability of 0.2 to
30.0 cc/cm.sup.2/sec.
[0081] In the long-fiber nonwoven fabric composing the support for
a separation membrane, a change rate between a thickness at a low
load and a thickness at a high load is preferably 0.00 to 0.03 mm.
The change rate in thicknesses is more preferably 0.00 to 0.02 mm,
and furthermore preferably 0.00 to 0.01 mm. Herein, the change rate
between a thickness at a low load and a thickness at a high load
refers to a difference between a thickness at the time of applying
a low load (load 2 kPa) with an indenter of 16 mm in diameter and a
thickness at the time of applying a high load (load 200 kPa) with
the same indenter. Particularly, a support of a separation membrane
such as a reverse osmosis membrane is subjected to a high reverse
osmotic pressure, and therefore it preferably has high rigidity
capable of standing a high pressure. Herein, preferable rigidity
refers to rigidity for standing a force applied vertically to the
separation membrane and avoiding distortion due to the force. When
the change rate between a thickness at a low load and a thickness
at a high load of the long-fiber nonwoven fabric is small, the
rigidity can be said to be a desired rigidity and the long-fiber
nonwoven fabric is suitable for the support for a separation
membrane.
[0082] When the change rate between a thickness at a low load and a
thickness at a high load of the long-fiber nonwoven fabric is 0.03
mm or less, distortions due to a pressure applied, particularly a
pressure partially applied, in using the long-fiber nonwoven fabric
as a support for a separation membrane are less, and therefore
membrane performance or a processing capacity can be retained.
[0083] The change rate between a thickness at a low load and a
thickness at a high load of the long-fiber nonwoven fabric refers
to a value measured by a method described in paragraph (10) in
Examples described later.
[0084] To obtain the long-fiber nonwoven fabric composing the
support for a separation membrane in which a change rate between a
thickness at a low load and a thickness at a high load of the
long-fiber nonwoven fabric is 0.00 to 0.03 mm, it is preferable to
use a complex-type filament, in which a low melting point polymer
having a melting point lower by 10 to 140.degree. C. than that of a
high melting point polymer is arranged about the high melting point
polymer, as a thermoplastic continuous filament composing the
long-fiber nonwoven fabric. Further, an aspect, in which an average
fiber diameter of thermoplastic continuous filaments composing the
long-fiber nonwoven fabric is set at 3 to 17 .mu.m and a long-fiber
nonwoven fabric obtained by a spunbonding method is unified in the
form of a sheet by thermocompression bonding, is preferable for
obtaining the long-fiber nonwoven fabric in which a change rate
between a thickness at a low load and a thickness at a high load is
0.00 to 0.03 mm.
[0085] Average surface roughness of the long-fiber nonwoven fabric
composing the support for a separation membrane is preferably 2 to
9 .mu.m. The average surface roughness is more preferably 2 to 8
.mu.m, and furthermore preferably 2 to 7 .mu.m. When the average
surface roughness of the long-fiber nonwoven fabric is 2 .mu.m or
more, it is rare that the surface of the nonwoven fabric is
extremely packed, and this causes an increase of pressure loss or
peeling of the separation membrane on the support when using the
nonwoven fabric as a support for a separation membrane. Further,
when the average surface roughness of the long-fiber nonwoven
fabric is 9 .mu.m or less, it is rare that formation of a
separation membrane becomes difficult when using the nonwoven
fabric as a support for a separation membrane.
[0086] The surface roughness of the long-fiber nonwoven fabric
refers to a value measured by a method described in paragraph (11)
in Examples described later.
[0087] To obtain the long-fiber nonwoven fabric composing the
support for a separation membrane in which the average surface
roughness is 2 to 9 .mu.m, it is preferable to thermocompression
bond long-fiber nonwoven fabrics with a pair of upper/lower flat
rolls to unify them. Further, an aspect, in which a complex-type
filament, in which a low melting point polymer having a melting
point lower by 10 to 140.degree. C. than that of a high melting
point polymer is arranged about the high melting point polymer, is
used as a thermoplastic continuous filament composing the
long-fiber nonwoven fabric and an average fiber diameter of
thermoplastic continuous filaments composing a long-fiber nonwoven
fabric is set at 3 to 17 .mu.m, is preferable for obtaining the
long-fiber nonwoven fabric in which the average surface roughness
is preferably 2 to 9 p.m.
[0088] In the long-fiber nonwoven fabric composing the support for
a separation membrane, both stresses of elongation of 5% in a
machine direction and a crosswise direction are preferably 50 to
500 N/5 cm. Both the stresses of elongation of 5% are more
preferably 70 to 500 N/5 cm, and furthermore preferably 90 to 500
N/5 cm. When both stresses of elongation of 5% in a machine
direction and a crosswise direction of the long-fiber nonwoven
fabric are 50 N/5 cm or more, this means that the long-fiber
nonwoven fabric is hardly distorted by any force applied to a
machine direction or a crosswise direction, and in the case where
the long-fiber nonwoven fabric is used as a support for a
separation membrane, the long-fiber nonwoven fabric stands a force
whichever direction the force is applied to, and it is possible to
suppress the depression of the separation membrane into a groove
even when a particularly high reverse osmotic pressure is applied
to the separation membrane. Further, when both the stresses of
elongation of 5% in a machine direction and a crosswise direction
of the long-fiber nonwoven fabric are 500 N/5 cm or less, it never
occurs that productivity and cost of the long-fiber nonwoven fabric
are significantly deteriorated, and handling of the long-fiber
nonwoven fabric hardly becomes difficult due to a too hard
sheet.
[0089] The stress of elongation of 5% of the long-fiber nonwoven
fabric refers to a value measured by a method described in
paragraph (12) in Examples described later.
[0090] To obtain the long-fiber nonwoven fabric composing the
support for a separation membrane in which both stresses of
elongation of 5% in a machine direction and a crosswise direction
are 50 to 500 N/5 cm, it is preferable to use the long-fiber
nonwoven fabric substantially comprising only spunbonded nonwoven
fabric(s) or to use a spunbonded nonwoven fabric for at least one
layer in a laminated body when the long-fiber nonwoven fabric is
the laminated body consisting of a plurality of nonwoven fabric
layers. Further, an aspect of using a complex-type filament, in
which a low melting point polymer having a melting point lower by
10 to 140.degree. C. than that of a high melting point polymer is
arranged about the high melting point polymer, is used as a
thermoplastic continuous filament composing the long-fiber nonwoven
fabric is also preferable for obtaining the long-fiber nonwoven
fabric in which both stresses of elongation of 5% in a machine
direction and a crosswise direction are 50 to 500 N/5 cm.
[0091] In the long-fiber nonwoven fabric composing the support for
a separation membrane, a ratio of stress of elongation of 5% in a
machine direction to stress of elongation of 5% in a crosswise
direction is preferably 1.0 to 2.7. The ratio between the machine
direction and the machine direction is more preferably 1.0 to 2.5,
and furthermore preferably 1.0 to 2.3. When the ratio of stress of
elongation of 5% in a machine direction to that in a crosswise
direction is 1.0 or more, it is possible to prevent the
productivity of the long-fiber nonwoven fabric from significantly
deteriorating. Further, when the ratio of stress of elongation of
5% in a machine direction to that in a crosswise direction is 2.7
or less, whichever direction a force is applied to, the separation
membrane stands the force, and it is possible to suppress the
depression of the separation membrane into a groove even when a
particularly high reverse osmotic pressure is applied to the
separation membrane.
[0092] The ratio of stress of elongation of 5% in a machine
direction to stress of elongation of 5% in a crosswise direction of
the long-fiber nonwoven fabric refers to a value measured by a
method described in paragraph (12) in Examples described later.
[0093] To obtain the long-fiber nonwoven fabric composing the
support for a separation membrane in which the ratio of stress of
elongation of 5% in a machine direction to stress of elongation of
5% in a crosswise direction is 1.0 to 2.7, it is preferable to use
the long-fiber nonwoven fabric substantially comprising only
spunbonded nonwoven fabric(s) or to use a spunbonded nonwoven
fabric for at least one layer in a laminated body when the
long-fiber nonwoven fabric is the laminated body consisting of a
plurality of nonwoven fabric layers. Further, an aspect of using a
complex-type filament, in which a low melting point polymer having
a melting point lower by 10 to 140.degree. C. than that of a high
melting point polymer is arranged about the high melting point
polymer, is used as a thermoplastic continuous filament composing
the long-fiber nonwoven fabric is also preferable for obtaining the
long-fiber nonwoven fabric in which a ratio of stress of elongation
of 5% in a machine direction to stress of elongation of 5% in a
crosswise direction is 1.0 to 2.7.
[0094] It is preferable that an average fiber diameter of
thermoplastic continuous filaments composing the long-fiber
nonwoven fabric is 3 to 17 p.m. The average fiber diameter is more
preferably 5 to 15 .mu.m, and furthermore preferably 7 to 14 .mu.m.
When an average fiber diameter of thermoplastic continuous
filaments is 3 .mu.m or more, since a spinning property is hardly
deteriorated during producing the long-fiber nonwoven fabric and
air permeability of the support for a separation membrane can be
maintained, peeling of a membrane in applying and spreading a
polymer solution is less and a good film-forming property can be
attained. On the other hand, when an average fiber diameter of
thermoplastic continuous filaments is 17 .mu.m or less, since the
long-fiber nonwoven fabric and the support for a separation
membrane, which are superior in uniformity, can be attained and the
support for a separation membrane can be more dense, excessive
permeation in applying and spreading a polymer solution is less and
an excellent film-forming property can be attained.
[0095] The average fiber diameter of thermoplastic continuous
filaments refers to a value measured by a method described in
paragraph (13) in Examples described later.
[0096] Weight per unit area of the long-fiber nonwoven fabric
composing the support for a separation membrane is preferably 20 to
150 g/m.sup.2. The weight per unit area is more preferably 30 to
120 g/m.sup.2, and furthermore preferably 40 to 90 g/m.sup.2. When
the weight per unit area is 20 g/m.sup.2 or more, excessive
permeation in applying and spreading a polymer solution is less and
an excellent film-forming property can be attained, and a
separation membrane having excellent mechanical strength and
excellent durability can be obtained. On the other hand, when the
weight per unit area is 150 g/m.sup.2 or less, a thickness of the
separation membrane can be reduced to increase an area of the
separation membrane per a fluid separation element unit.
[0097] The weight per unit area of the long-fiber nonwoven fabric
refers to a value measured by a method described in paragraph (6)
in Examples described later.
[0098] A thickness of the long-fiber nonwoven fabric composing the
support for a separation membrane is preferably 0.03 to 0.20 mm.
The thickness is more preferably 0.04 to 0.16 mm, and furthermore
preferably 0.05 to 0.12 mm. When the thickness of the long-fiber
nonwoven fabric is 0.03 mm or more, excessive permeation in
applying and spreading a polymer solution is less and an excellent
film-forming property can be attained, and a separation membrane
having excellent mechanical strength and excellent durability can
be obtained. On the other hand, when the thickness of the
long-fiber nonwoven fabric is 0.20 mm or less, a thickness of the
separation membrane can be reduced to increase an area of the
separation membrane per a fluid separation element unit.
[0099] The thickness of the long-fiber nonwoven fabric refers to a
value measured by a method described in paragraph (7)A in Examples
described later.
[0100] Next, a method for producing the long-fiber nonwoven fabric
composing the support for a separation membrane will be
described.
[0101] The long-fiber nonwoven fabric can provide a separation
membrane which exhibits an excellent film-forming property in
forming the separation membrane on a support and has excellent
durability, and it can be preferably produced by a spunbonding
method or a melt blowing method.
[0102] The spunbonding method is a method in which a melted
thermoplastic polymer is extruded and drawn by suction of a high
speed suction gas to be spun into fibers, and then the resulting
fibers were collected on a moving conveyer to form fibrous webs,
and the fibrous webs are successively subjected to
thermocompression bonding and entangled bonding to form a
sheet-like unified long-fiber nonwoven fabric. In the case of the
spunbonding method, a spinning speed is preferably 2000 m/min or
more to highly orient and crystallize constituent fibers. The
spinning speed is more preferably 3000 m/min or more, and
furthermore preferably 4000 m/min or more. In the case of bringing
thermoplastic continuous filaments into a complex form of a
core-sheath type, a common method for forming a complex can be
employed.
[0103] The melt blowing method is a method in which by blowing a
heated high speed gas stream on a melted thermoplastic polymer, the
thermoplastic polymer is drawn into an extra-fine fiber and the
extra-fine fibers are collected to form a sheet-like long-fiber
nonwoven fabric.
[0104] Furthermore, to obtain a separation membrane having a good
film-forming property and excellent mechanical strength and
excellent durability in forming a separation membrane, it is
preferable to unify a long-fiber nonwoven fabric obtained by a
spunbonding method in the form of a sheet by thermocompression
bonding from the viewpoint of suppressing fuzz. As a means of
unifying, there is a method of thermocompression bonding long-fiber
nonwoven fabrics with a pair of upper/lower flat rolls to unify
them. This flat roll is a metal roll or an elastic roll which is
not provided with pits and projections on the surface of the roll.
The metal roll and another metal roll can be used in a pair, or the
metal roll and the elastic roll can be used in a pair.
Particularly, since by inhibiting the fusion of fibers at the
surface of the long-fiber non-woven fabric to maintain a form of
the nonwoven fabric, an anchoring effect of suppressing peeling of
the separation membrane is achieved when using the nonwoven fabric
as a support for a separation membrane, a method, in which the
long-fiber nonwoven fabric is thermocompression bonded with a
heated metal roll and an elastic roll not heated, is preferably
employed.
[0105] The elastic roll refers to a roll made of a material having
elasticity compared with the metal roll. Examples of materials of
the elastic roll include paper, cotton and aramide paper (so-called
paper roll), and include an urethane resin, an epoxy resin, a
silicon resin and hard rubber (resin roll).
[0106] A temperature of a heated flat roll is preferably lower by
80 to 20.degree. C. than a melting point of a polymer composing at
least the surface of thermoplastic continuous filament composing
the long-fiber nonwoven fabric, and more preferably lower by 60 to
30.degree. C. Further, in the case of the complex-type filament
made of polymers having different melting points, in which a low
melting point polymer having a melting point lower by 10 to
140.degree. C. than that of a high melting point polymer is
arranged about the high melting point polymer, a temperature of the
flat roll is preferably lower by 80 to 20.degree. C. than a melting
point of the low melting point polymer, and more preferably lower
by 60 to 30.degree. C.
[0107] Furthermore, it is preferable that a temperature difference
is made between upper/lower flat rolls, and a temperature of flat
roll on a high-temperature side is set at a temperature lower by 80
to 20.degree. C. than a melting point of a polymer composing the
surface of thermoplastic continuous filament composing the
long-fiber nonwoven fabric and a temperature of flat roll on a
low-temperature side is set at a temperature lower by 40 to
120.degree. C. than that of the flat roll on a high-temperature
side. When the temperature difference between the flat roll on a
low-temperature side and the flat roll on a high-temperature side
is 40.degree. C. or more, formation of an extremely high density
portion at the surface of the long-fiber nonwoven fabric can be
suppressed, and peeling of a membrane due to insufficient
permeation in applying and spreading a polymer solution is less and
a good film-forming property can be attained. On the other hand,
when the temperature difference between the flat roll on a
low-temperature side and the flat roll on a high-temperature side
is 120.degree. C. or less, delamination of the laminated long-fiber
nonwoven fabric can be suppressed, and excessive permeation in
applying and spreading a polymer solution is less and an excellent
film-forming property can be attained. The temperature of flat roll
on a high-temperature side is more preferably set at a temperature
lower by 60 to 30.degree. C. than a melting point of a polymer
composing the surface of thermoplastic continuous filament
composing the long-fiber nonwoven fabric. Further, the temperature
of flat roll on a low-temperature side is more preferably set at a
temperature lower by 60 to 100.degree. C. than that of flat roll on
a high-temperature side.
[0108] Further, a line pressure of the flat rolls is preferably 20
to 500 kg/cm. The line pressure is more preferably 50 to 500 kg/cm,
and furthermore preferably 100 to 500 kg/cm. When the line pressure
of the flat rolls is 20 kg/cm or more, delamination of the
laminated long-fiber nonwoven fabric can be suppressed, and
excessive permeation in applying and spreading a polymer solution
is less and an excellent film-forming property can be attained. On
the other hand, when the line pressure of the flat rolls is 500
kg/cm or less, formation of an extremely high density portion at
the surface of the long-fiber nonwoven fabric can be suppressed,
and peeling of a membrane due to insufficient permeation in
applying and spreading a polymer solution is less and a good
film-forming property can be attained.
[0109] Further, instead of a method of thermocompression bonding
long-fiber nonwoven fabrics with only a pair of flat rolls, a
method of bonding the long-fiber nonwoven fabrics in two steps to
more precisely control the characteristics of the long-fiber
nonwoven fabric can also be employed. That is, a two step bonding
method, in which the long-fiber nonwoven fabrics are preliminarily
thermocompression bonded between a pair of flat rolls or between
one flat roll and a collecting conveyor used for collecting fibrous
web to obtain a long-fiber nonwoven fabric in a state of temporary
bonding, and then in a continuous step or after the long-fiber
nonwoven fabric in a state of temporary bonding is taken up, the
long-fiber nonwoven fabrics are thermocompression bonded again
between flat rolls, can also be employed. In the preliminary
thermocompression bonding at a first step in the two step bonding
method, a packed density of the long-fiber nonwoven fabric in a
state of temporary bonding is preferably set at 0.1 to 0.3 since
the long-fiber nonwoven fabric can be more dense during the
thermocompression bonding at a second step. In doing so, a
temperature of flat rolls used for pre-thermocompression bonding in
the first step is preferably lower by 120 to 20.degree. C. than a
melting point of a fiber composing the long-fiber nonwoven fabric,
and a line pressure of the flat rolls is preferably 5 to 70
kg/cm.
[0110] Further, in the case of the laminated long-fiber nonwoven
fabric, by forming a high-density layer at an interface between
laminated layers, it is possible that excessive permeation in
applying and spreading a polymer solution is less and an excellent
film-forming property is attained. From this, a method, in which
long-fiber nonwoven fabrics composed of thermoplastic continuous
filaments are preliminarily thermocompression bonded between a pair
of upper/lower flat rolls, or between one flat roll and a
collecting conveyor used for collecting fibrous web, and in a
continuous step or after the nonwoven fabric in a state of
temporary bonding, in which a high-density layer is formed on a
surface side and/or a backside, is taken up, plural sheets of the
nonwoven fabric in a state of temporary bonding, preliminarily
thermocompression bonded, are superimposed on one another, and the
resulting laminated body is thermocompression bonded again between
a pair of upper/lower flat rolls and unified, is preferably
used.
[0111] Herein, a temperature of the flat roll in obtaining the
nonwoven fabric in a state of temporary bonding, preliminarily
thermocompression bonded, is preferably lower by 120 to 20.degree.
C. than a melting point of the thermoplastic continuous filament,
and more preferably lower by 100 to 40.degree. C. When a difference
between the temperature of the flat roll and the melting point of
the thermoplastic continuous filament is 120.degree. C. or less, a
high-density layer can be formed on a surface side and/or a
backside of the long-fiber nonwoven fabric. Further, when the
difference is 20.degree. C. or more, it never occurs the fusing on
a surface side and/or a backside of the long-fiber nonwoven fabric
proceeds excessively to make it difficult to unify the long-fiber
nonwoven fabric.
[0112] Further, a line pressure in obtaining the nonwoven fabric in
a state of temporary bonding, preliminarily thermocompression
bonded, is preferably 5 to 70 kg/cm, and more preferably 10 to 60
kg/cm.
[0113] As described above, the long-fiber nonwoven fabric composing
the support for a separation membrane may be a long-fiber nonwoven
fabric comprising a single layer, but a laminated body comprising a
plurality of long-fiber nonwoven fabric layers is also a preferable
form since a support for a separation membrane which is more
superior in uniformity can be obtained. As a method for producing a
laminated body comprising two layers of spunbonded nonwoven fabrics
as a laminated body, a method, in which two sheets of the
spunbonded nonwoven fabrics in a state of temporary bonding,
obtained by preliminarily thermocompression bonding between a pair
of flat rolls by the above-mentioned two step bonding method, are
superimposed on one another, and then thermocompression bonded
again between flat rolls, is preferably employed.
[0114] Further, as a method for producing a laminated body of a
three-layer structure formed by interposing a melt blowing layer
between two-layered spunbonded nonwoven fabric layers, a method, in
which a melt blowing nonwoven fabric produced in another line is
added in a manner of interposing between two layers of the
spunbonded nonwoven fabrics in a state of temporary bonding,
obtained by preliminarily thermocompression bonding between a pair
of flat rolls by the above-mentioned two step bonding method, and
then the nonwoven fabric of the three-layer structure is
thermocompression bonded again between flat rolls, is adopted.
[0115] Further, as another method for producing a laminated body of
a three-layer structure, a method, in which fibrous webs extruded
from a nozzle for spunbonding, a nozzle for melt blowing and a
nozzle for spunbonding, located above a series of collecting
conveyers, respectively, and fibrosed are successively collected,
laminated and thermocompression bonded, can be employed.
[0116] Furthermore, as another method for producing a laminated
body of a three-layer structure, a method, in which fibrous webs
extruded from a nozzle for spunbonding, a nozzle for melt blowing
and a nozzle for spunbonding, located above a series of collecting
conveyers, respectively, and fibrosed are successively collected
and laminated, and the resulting laminated fibrous webs are
preliminarily thermocompression bonded between a flat roll placed
on a collecting conveyer and the conveyor, and in a continuous step
or after a sheet in a state of temporary bonding is produced and
taken up, the sheet is thermocompression bonded again between a
pair of flat rolls, can also be preferably employed.
[0117] The long-fiber nonwoven fabric produced by a melt blowing
method can be produced by blowing a heated high speed gas stream on
a melted thermoplastic polymer to draw the thermoplastic polymer
into an extra-fine fiber and collecting the extra-fine fiber to
form a sheet.
[0118] The separation membrane is a separation membrane formed by
forming a membrane having a separation function on the
above-mentioned support for a separation membrane. Examples of such
a separation membrane include semipermeable membrane such as a
microfiltration membrane, an ultrafiltration membrane, a
nanofiltration membrane and a reverse osmotic membrane. As a method
for producing of a separation membrane, a method of applying and
spreading a polymer solution on at least one surface of the support
for a separation membrane to form a membrane having a separation
function to obtain a separation membrane is preferably used.
Further, in the case where the separation membrane is a
semipermeable membrane, a form, in which the membrane having a
separation function is brought into a complex-type membrane
including a supporting layer and a semipermeable membrane layer,
and this complex-type membrane is laminated on at least one surface
of the support for a separation membrane, is also preferable. In
this case, the supporting layer does not have to have the
separation function.
[0119] The polymer solution applied and spread on the support for a
separation membrane comes to have a separation function at the time
of becoming a membrane, and for example, solutions of polysulfone,
polyarylethersulfone such as polyethersulfone, polyimide,
poly(vinylidene fluoride), or cellulose acetate are preferably
used. Among others, solutions of polysulfone and
polyarylethersulfone are preferably used in point of chemical
stability, mechanical stability and thermal stability. A solvent
can be appropriately selected in accordance with a material for
forming a membrane. Further, as a semipermeable membrane in the
case where the separation membrane is a complex-type membrane
including a supporting layer and a semipermeable membrane layer, a
membrane of crosslinked polyamide, which is obtained by
polycondensation of polyfunctional acid halide and polyfunctional
amine, is preferably used.
[0120] The fluid separation element refers to a fluid separation
element in which the separation membrane is housed in a case for
convenience of handling. Examples of its configuration include a
plate frame type of a plain membrane, a pleat-shaped type, and a
spiral type. Among others, the spiral type element, in which the
separation membrane is wound in a spiral fashion around a water
collecting pipe together with the material of a permeated liquid
flow passage and a material of a feed liquid flow passage, is
preferably employed. Further, a plurality of fluid separation
elements may be connected in series or in parallel to form a
separation membrane unit.
EXAMPLES
[0121] Next, our membranes and methods will be described
specifically by way of examples, but this disclosure is not limited
to these examples. Characteristic values of the aforementioned
support for a separation membrane, long-fiber nonwoven fabric
composing the support for a separation membrane and thermoplastic
continuous filaments composing the long-fiber non-woven fabric, and
characteristic values in the following examples are measured by the
following methods.
(1) Melting Point of Resin (.degree. C.)
[0122] Measurement was performed at a temperature raising speed of
20.degree. C./min using a differential scanning calorimeter DSC-2
manufactured by PerkinElmer Japan Co Ltd. and a temperature taking
an extremum in a melting endothermic curve obtained was considered
as a melting point of a resin. Further, as for a resin, a melting
endothermic curve of which does not exhibit an extremum in the
differential scanning calorimeter, the resin was heated on a hot
plate and a temperature at which melting of the resin was observed
with a microscope was considered as a melting point of the
resin.
(2) Intrinsic Viscosity IV of Resin
[0123] Intrinsic viscosity IV of a polyethylene terephthalate resin
was measured by the following method.
[0124] 8 g of sample was dissolved in 100 ml of o-chlorophenol, and
relative viscosity .eta..sub.r was determined from the following
equation:
.eta..sub.r=.eta./.eta..sub.0=(t.times.d)/(t.sub.0.times.d.sub.0),
[0125] using a Ostwald viscometer at 25.degree. C., [0126] .eta.:
viscosity of a polymer solution, [0127] .eta..sub.0: viscosity of
o-chlorophenol [0128] t: falling time of a solution (sec), [0129]
d: density of a solution (g/cm.sup.3) [0130] t.sub.0: falling time
of o-chlorophenol (sec), and [0131] d.sub.0: density of
o-chlorophenol (g/cm.sup.3).
[0132] Next, the intrinsic viscosity IV of the resin was calculated
from the following equation based on the relative viscosity
.eta..sub.r:
IV=0.0242 .eta..sub.r+0.2634.
(3) Tensile Strength (N/5 cm) and Tensile Elongation (%) of
Long-Fiber Nonwoven Fabric (%)
[0133] According to 5.3.1 of JIS L 1906 (2000), tensile strength
and tensile elongation were measured on five locations in
long-fiber nonwoven fabric samples with a size of 5 cm.times.30 cm
for each of a test in a vertical direction and a test in a lateral
direction under the conditions of a chuck distance of 20 cm and a
tensile speed of 10 cm/min, and strength and elongation at the time
of stretching the sample to break were read out. Measurements were
rounded off to unit and the resulting values were considered as
tensile strength and tensile elongation in a machine direction (MD)
and in a crosswise direction (CD). Further, a ratio of tensile
strength in a machine direction to tensile strength in a crosswise
direction was determined by dividing the tensile strength in a
machine direction by the tensile strength in a crosswise direction
and rounding off the resulting value to one decimal place.
(4) Product of Tensile Strength and Tensile Elongation of
Long-Fiber Nonwoven Fabric (N/5 cm)
[0134] Based on tensile strength and tensile elongation in a
machine direction (MD) and in a crosswise direction (CD) measured
in the above paragraph (3), a product of tensile strength and
tensile elongation was calculated by the following equation and the
resulting value were rounded off to unit, and the resulting values
were considered as a product of tensile strength and tensile
elongation in a machine direction (MD) and in a crosswise direction
(CD):
Product of tensile strength and tensile elongation[N/5 cm]=tensile
strength[N/5 cm].times.(1+tensile elongation[%]/100).
(5) Coefficient Of Variance Of Luminance Of Transmitted Light Of
Long-Fiber Nonwoven Fabric (%)
[0135] Three long-fiber nonwoven fabric samples with a size of 10
cm.times.10 cm were extracted, and these samples were superimposed
on one another against a black drawing paper and set in a scanner
(GT-X750 manufactured by SEIKO EPSON CORP.) and read at resolution
of 1200 dpi by the image scanner. Moreover, read image files was
processed by an image processing software (AT-Image Ver. 3.2) to
quantify an average of luminance. Coefficient of variance of
luminance of transmitted light was determined from a standard
deviation of the average value and rounded off to one decimal
place.
(6) Weight Per Unit Area of Long-Fiber Nonwoven Fabric
(g/m.sup.2)
[0136] Three long-fiber nonwoven fabric samples with a size of 30
cm.times.50 cm were extracted and each sample was weighed, and an
average of the obtained weight values was converted to a weight per
unit area and the converted value was rounded off to unit.
(7) Thickness of Long-Fiber Nonwoven Fabric (mm)
A. Thickness at Normal Load
[0137] According to 5.1 of JIS L 1906 (2000), thicknesses of 10
locations equally spaced per 1 m length in a width direction of a
long-fiber nonwoven fabric were measured in hundredth of a
millimeter, applying a load of 10 kPa by use of an indenter of 10
mm in diameter, and an average value of measurements was rounded
off to two decimal places.
B. Thickness at Low Load
[0138] Thicknesses of arbitrary 15 locations in a long-fiber
nonwoven fabric having a size of 30 cm.times.50 cm were measured in
hundredth of a millimeter, applying a load of 2 kPa by use of an
indenter of 16 mm in diameter, and an average value of measurements
was rounded off to two decimal places.
C. Thickness at High Load
[0139] Thicknesses of arbitrary 15 locations in a long-fiber
nonwoven fabric having a size of 30 cm.times.50 cm were measured in
hundredth of a millimeter, applying a load of 200 kPa by use of an
indenter of 16 mm in diameter, and an average value of measurements
was rounded off to two decimal places.
(8) Packed Density of Long-Fiber Nonwoven Fabric
[0140] Based on weight per unit area (g/m.sup.2) and a thickness
(mm) at a normal load, which are determined in the above paragraphs
(6) and (7)A, respectively, and a polymer (resin) density, a packed
density was calculated by the following equation and the resulting
value were rounded off to one decimal places:
Packed density=weight per unit area(g/m.sup.2)/thickness
(mm)/10.sup.3/polymer density(g/cm.sup.3).
(9) Air Permeability of Long-Fiber Nonwoven Fabric
(cc/cm.sup.2/sec)
[0141] Air permeability of arbitrary 45 points in a long-fiber
nonwoven fabric of 30 cm.times.50 cm was measured at a pressure of
125 Pa by a barometer according to 4.8 (1) fragile-type method of
JIS L 1906 (2000). An average value of measurements was rounded off
to one decimal place.
(10) Change Rate Between Thickness at Low Load and Thickness at
High Load of Long-Fiber Nonwoven Fabric (mm)
[0142] A value obtained by subtracting the thickness (mm) at a high
load determined in the above paragraph (7)C from the thickness (mm)
at a low load determined in the above paragraph (7)B was taken as a
change rate between a thickness at a low load and a thickness at a
high load.
(11) Average Surface Roughness Ra of Long-Fiber Nonwoven Fabric
(.mu.m)
[0143] According to definition described in 3.1 of JIS B 0601
(1994), average surface roughness Ra (arithmetic mean) was
determined using Surf Corder SE-40C manufactured by Kosaka
Laboratory Ltd. Measurement was performed under the conditions of a
cut off value 2.5 mm, an evaluation length 12.5 mm and a measuring
speed 0.5 mm/s for two cases where a length direction (lengthwise)
of a long-fiber nonwoven fabric samples with a size of 30
cm.times.50 cm is an evaluation length direction and a width
direction (crosswise) of a long-fiber nonwoven fabric samples is an
evaluation length direction, and number of measuring locations per
one direction is 10 for each of a front side and a back side, and
therefore 40 locations were measured. An average was rounded off so
as to have one significant figure, and the resulting value was
taken as surface roughness Ra (.mu.m).
(12) Stress of Elongation of 5% of Long-Fiber Nonwoven Fabric (N/5
cm)
[0144] According to 5.3.1 of JIS L 1906 (2000), tensile strength
and tensile elongation were measured on five locations in
long-fiber nonwoven fabric samples with a size of 5 cm.times.30 cm
for each of a test in a vertical direction and a test in a lateral
direction under the conditions of a chuck distance of 20 cm and a
tensile speed of 10 cm/min, and stress of elongation of 5% was read
out from the resulting tensile strength/tensile elongation curve,
and these stress values were rounded off to unit and the resulting
values were considered as stress of elongation of 5% in a machine
direction (MD) and in a crosswise direction (CD). Further, a ratio
of tensile strength in a machine direction to tensile strength in a
crosswise direction was determined by dividing the tensile strength
in a machine direction by the tensile strength in a crosswise
direction and rounding off the resulting value to one decimal
place.
(13) Fiber Diameter (.mu.m)
[0145] Ten small samples are extracted at random from the
long-fiber nonwoven fabric and photographs of magnifications of 500
to 3000 times are taken with a scanning electron microscope, and 10
fibers per each sample, 100 fibers in total, are selected at random
to measure its fiber diameter. A fiber diameter was determined by
rounding off an average of these fiber diameters to unit.
(14) Degree of Strike Through of Cast Liquid During Film
Formation
Reverse Osmosis Membrane for Seawater Desalination
[0146] On each support for a separation membrane, 15% by weight
dimethylformamide solution (cast liquid) of polysulfone
("Udel"(registered trade mark)-P3500 manufactured by SOLVAY
Advanced Polymers Co., Ltd.) was casted in a thickness of 50 .mu.m
at room temperature (20.degree. C.), and immediately the support
for a separation membrane was dipped into pure water at room
temperature (20.degree. C.) and left standing for 5 minutes to
prepare a separation membrane made of polysulfone.
[0147] Next, a backside of the prepared reverse osmosis membrane
was visually observed, and a degree of strike through of a cast
liquid was rated on the following scale of 1 to 5. Score 4 or more
means acceptance. [0148] Score 5: There is no strike through of a
cast liquid. [0149] Score 4: There is a little strike through of a
cast liquid (area ratio less than 5%). [0150] Score 3: There is
strike through of a cast liquid (area ratio between 5% and 50%).
[0151] Score 2: There is strike through of a cast liquid in most
area (area ratio between 51% and 80%). [0152] Score 1: There is
strike through of a cast liquid in almost whole area.
(15) Depression Rate of Separation Membrane (.mu.m)
[0153] Using a material of a feed liquid flow passage comprising
mesh-like fabric, the above-mentioned reverse osmosis membrane for
seawater desalination, a pressure-proof sheet, and the following
material of a permeated liquid flow passage, a spiral type fluid
separation element having an effective area of 40 m.sup.2 was
prepared.
Material of a Permeated Liquid Flow Passage
[0154] A polyester single tricot in which a groove width is 200
.mu.m, a groove depth is 150 .mu.m, groove density is 40/inch, and
a thickness is 200 .mu.m, was used.
[0155] Next, a durability test of the prepared fluid separation
element was prepared under the conditions of a reverse osmotic
pressure of 7 MPa, a salt concentration of sea water of 3% by
weight and operation temperature 40.degree. C., and after 1000
hours operation, the fluid separation element was disassembled and
a depression rate of a separation membrane into the material of a
permeated liquid flow passage was measured. Photographs of
separation membrane cross sections of arbitrary 3 locations of a
fluid separation element were taken at a magnification of 500 to
3000 times with a scanning electron microscope and to measure the
depression rate (unit: .mu.m). An average of measurements was
rounded off to unit to determine the depression rate. With respect
to a direction in which the support for a separation membrane is
superimposed on the material of a permeated liquid flow passage,
test was performed with two directions; that is, a nonwoven fabric
length direction (lengthwise) of the support for a separation
membrane is orthogonal to a groove direction of the material of a
permeated liquid flow passage, and a nonwoven fabric width
direction (crosswise) of the support for a separation membrane is
orthogonal to a groove direction of the material of a permeated
liquid flow passage.
Example 1
[0156] A polyethylene terephthalate (PET) resin (a) having
intrinsic viscosity IV of 0.65 and a melting point of 260.degree.
C., which was dried to a water content of 50 ppm or less and
contains 0.3% by weight of titanium oxide, and a copolymerization
polyester resin (b) having intrinsic viscosity IV of 0.66 and a
melting point of 230.degree. C., which was dried to a water content
of 50 ppm or less and contains 0.2% by weight of titanium oxide, in
which a copolymerization ratio of isophthalic acid was 10 mole %,
were prepared.
[0157] The above-mentioned polyethylene terephthalate resin (a) and
copolymerization polyester resin (b) were melted at 295.degree. C.
and 280.degree. C., respectively. These polyethylene terephthalate
resin (a) and copolymerization polyester resin (b) were extruded
from a pore as a core component and a sheath component,
respectively, at a nozzle temperature of 300.degree. C. in
proportions of the core and the sheath of 80:20 by weight, and
these components were spun into concentric filaments of a
core-sheath type having a circular cross section at a spinning
speed of 4300 m/min with an ejector, and the resulting filaments
were collected as a fibrous web on a moving net conveyor. The
collected fibrous web was supported between a pair of upper/lower
steel flat rolls and thermocompression bonded at a line pressure of
60 kg/cm by the flat rolls whose surface temperatures were
190.degree. C. to produce a spunbonded nonwoven fabric in which a
fiber diameter of a continuous filament was 11 .mu.m, weight per
unit area was 80 g/m.sup.2 and a thickness was 0.11 mm to obtain a
support for a separation membrane. The results are shown in Table
1.
Example 2
[0158] The polyethylene terephthalate resin (a) and the
copolymerization polyester resin (b), which were used in Example 1,
were melted at 295.degree. C. and 280.degree. C., respectively.
These polyethylene terephthalate resin (a) and copolymerization
polyester resin (b) were extruded from a pore as a core component
and a sheath component, respectively, at a nozzle temperature of
300.degree. C. in proportions of the core and the sheath of 80:20
by weight, and these components were spun into concentric filaments
of a core-sheath type having a circular cross section at a spinning
speed of 4500 m/min with an ejector, and the resulting filaments
were collected as a fibrous web on a moving net conveyor. The
collected fibrous web was supported between a pair of upper/lower
steel flat rolls and thermocompression bonded at a line pressure of
60 kg/cm by the flat rolls whose surface temperatures were
190.degree. C. to produce a spunbonded nonwoven fabric in which a
fiber diameter of a continuous filament was 10 .mu.m, weight per
unit area was 80 g/m.sup.2 and a thickness was 0.10 mm to obtain a
support for a separation membrane. The results are shown in Table
1.
Example 3
[0159] The polyethylene terephthalate resin (a) and the
copolymerization polyester resin (b), which were used in Example 1,
were melted at 295.degree. C. and 280.degree. C., respectively.
These polyethylene terephthalate resin (a) and copolymerization
polyester resin (b) were extruded from a pore as a core component
and a sheath component, respectively, at a nozzle temperature of
300.degree. C. in proportions of the core and the sheath of 85:15
by weight, and these components were spun into concentric filaments
of a core-sheath type having a circular cross section at a spinning
speed of 4300 m/min with an ejector, and the resulting filaments
were collected as a fibrous web on a moving net conveyor. The
collected fibrous web was supported between a pair of upper/lower
steel flat rolls and thermocompression bonded at a line pressure of
60 kg/cm by the flat rolls whose surface temperatures were
190.degree. C. to produce a spunbonded nonwoven fabric in which a
fiber diameter of a continuous filament was 11 .mu.m, weight per
unit area was 50 g/m.sup.2 and a thickness was 0.08 mm to obtain a
support for a separation membrane. The results are shown in Table
1.
Example 4
[0160] The polyethylene terephthalate resin (a) and the
copolymerization polyester resin (b), which were used in Example 1,
were melted at 295.degree. C. and 280.degree. C., respectively.
These polyethylene terephthalate resin (a) and copolymerization
polyester resin (b) were extruded from a pore as a core component
and a sheath component, respectively, at a nozzle temperature of
300.degree. C. in proportions of the core and the sheath of 80:20
by weight, and these components were spun into concentric filaments
of a core-sheath type having a circular cross section at a spinning
speed of 4500 m/min with an ejector, and the resulting filaments
were collected as a fibrous web on a moving net conveyor. The
collected fibrous web was supported between a pair of upper/lower
steel flat rolls and preliminarily thermocompression bonded at a
line pressure of 60 kg/cm by the flat rolls whose surface
temperatures were 140.degree. C. to produce a spunbonded nonwoven
fabric in which a fiber diameter of a continuous filament was 10
.mu.m, weight per unit area was 70 g/m.sup.2 and a thickness was
0.25 mm.
[0161] The obtained spunbonded nonwoven fabric was supported
between a pair of flat rolls in which an upper flat roll was made
of steel and a lower flat roll was made of an urethane resin, and
after only the upper flat roll was heated so that its surface
temperature was 170.degree. C. and a surface temperature of the
resin roll was stabilized at 100.degree. C., the spunbonded
nonwovens was further thermocompression bonded at a line pressure
of 170 kg/cm to produce a spunbonded non-woven fabric in which
weight per unit area was 70 g/m.sup.2 and a thickness was 0.10 mm
to obtain a support for a separation membrane. The results are
shown in Table 1.
TABLE-US-00001 TABLE 1 Example 1 Example 2 Example 3 Example 4
Resin*.sup.1 PET/co-PET PET/co-PET PET/co-PET PET/co-PET Species of
sheet Spunbonded Spunbonded Spunbonded Spunbonded nonwoven nonwoven
nonwoven nonwoven fabric fabric fabric fabric Spinning speed
(m/min) 4300 4500 4300 4500 Number of layers 1 1 1 1 Bonding method
one step one step one step two step Thermo- Species of roll steel/
steel/ steel/ steel/ compression upper/lower steel steel steel
resin bonding Surface temperature 190/190 190/190 190/190 170/100
roll upper/lower (.degree. C.) Line pressure 60 60 60 170 (kg/cm)
Fiber diameter (.mu.m) 11 10 11 10 Weight per unit area (g/m.sup.2)
80 80 50 70 Thickness at normal load 0.11 0.10 0.08 0.10 (mm) at
low load 0.12 0.11 0.09 0.11 at high load 0.11 0.10 0.08 0.10
Change rate of thickness (mm) 0.01 0.01 0.01 0.01 Density
(g/cm.sup.3) 0.7 0.8 0.6 0.7 Packed density 0.5 0.6 0.5 0.5 Tensile
Machine 415 419 230 387 strength direction (MD) (N/5 cm) Crosswise
178 197 105 178 direction (CD) Ratio of machine 2.3 2.1 2.2 2.2
direction to crosswise direction Tensile Machine 23 23 25 29
elongation direction (MD) (%) Crosswise 18 22 20 24 direction (CD)
Product of Machine 510 515 288 499 tensile direction (MD) strength
Crosswise 210 240 126 221 and tensile direction (CD) elongation
(N/5 cm) Stress of Machine 260 263 136 230 elongation direction
(MD) of 5% Crosswise 140 158 73 119 (N/5 cm) direction (CD) Ratio
of machine 1.9 1.7 1.9 1.9 direction to crosswise direction
Coefficient of variance of 4.4 4.2 4.6 4.3 luminance of transmitted
light (%) Air permeability (cc/cm.sup.2/sec) 2.0 1.8 8.9 2.5
Surface roughness Ra (.mu.m) 4 4 4 4 Degree of strike through of
cast 4 4 4 4 liquid during film formation (number of points)
Depression Machine direction of 25 25 32 28 rate of nonwoven fabric
separation Crosswise direction 33 32 38 36 membrane of nonwoven
fabric (.mu.m) *.sup.1PET: polyethylene terephthalate, co-PET:
copolymerization polyethylene terephthalate
Example 5
[0162] The polyethylene terephthalate resin (a) and the
copolymerization polyester resin (b), which were used in Example 1,
were melted at 295.degree. C. and 280.degree. C., respectively.
These polyethylene terephthalate resin (a) and copolymerization
polyester resin (b) were extruded from a pore as a core component
and a sheath component, respectively, at a nozzle temperature of
300.degree. C. in proportions of the core and the sheath of 80:20
by weight, and these components were spun into concentric filaments
of a core-sheath type having a circular cross section at a spinning
speed of 4500 m/min with an ejector, and the resulting filaments
were collected as a fibrous web on a moving net conveyor. The
collected fibrous web was supported between a pair of upper/lower
steel flat rolls and preliminarily thermocompression bonded at a
line pressure of 60 kg/cm by the flat rolls whose surface
temperatures were 140.degree. C. to produce a spunbonded non-woven
fabric in which a fiber diameter of a continuous filament was 10
.mu.m, weight per unit area was 75 g/m.sup.2 and a thickness was
0.38 mm.
[0163] The obtained spunbonded nonwoven fabric was supported
between a pair of upper/lower steel flat rolls, and after the flat
rolls were heated so that a surface temperature of the upper steel
flat roll was 170.degree. C. and a surface temperature of the lower
steel flat roll was 90.degree. C., the spunbonded nonwoven was
thermocompression bonded at a line pressure of 170 kg/cm to produce
a spunbonded nonwoven fabric in which weight per unit area was 75
g/m.sup.2 and a thickness was 0.10 mm to obtain a support for a
separation membrane. The results are shown in Table 2.
Example 6
[0164] The polyethylene terephthalate resin (a) and the
copolymerization polyester resin (b), which were used in Example 1,
were melted at 295.degree. C. and 280.degree. C., respectively.
These polyethylene terephthalate resin (a) and copolymerization
polyester resin (b) were extruded from a pore as a core component
and a sheath component, respectively, at a nozzle temperature of
300.degree. C. in proportions of the core and the sheath of 80:20
by weight, and these components were spun into concentric filaments
of a core-sheath type having a circular cross section at a spinning
speed of 4500 m/min with an ejector, and the resulting filaments
were collected as a fibrous web on a moving net conveyor. The
collected fibrous web was supported between a pair of upper/lower
steel flat rolls and preliminarily thermocompression bonded at a
line pressure of 60 kg/cm by the flat rolls whose surface
temperatures were 140.degree. C. to produce a spunbonded non-woven
fabric in which a fiber diameter of a continuous filament was 10
.mu.m, weight per unit area was 35 g/m.sup.2 and a thickness was
0.15 mm.
[0165] Two sheets of the obtained spunbonded nonwoven fabrics were
superimposed on each other, and the superimposed spunbonded
nonwovens were supported between a pair of flat rolls in which an
upper flat roll was made of steel and a lower flat roll was made of
an urethane resin, and after only the upper flat roll was heated to
170.degree. C. and a surface temperature of the resin flat roll was
stabilized at 100.degree. C., the superimposed spunbonded nonwovens
were further thermocompression bonded at a line pressure of 170
kg/cm to produce a spunbonded nonwoven fabric in which weight per
unit area was 70 g/m.sup.2 and a thickness was 0.10 mm to obtain a
support for a separation membrane. The results are shown in Table
2.
Example 7
[0166] The polyethylene terephthalate resin (a) and the
copolymerization polyester resin (b), which were used in Example 1,
were melted at 295.degree. C. and 280.degree. C., respectively.
These polyethylene terephthalate resin (a) and copolymerization
polyester resin (b) were extruded from a pore as a core component
and a sheath component, respectively, at a nozzle temperature of
300.degree. C. in proportions of the core and the sheath of 80:20
by weight, and these components were spun into concentric filaments
of a core-sheath type having a circular cross section at a spinning
speed of 4500 m/min with an ejector, and the resulting filaments
were collected as a fibrous web on a moving net conveyor. The
collected fibrous web was supported between a pair of upper/lower
steel flat rolls and preliminarily thermocompression bonded at a
line pressure of 60 kg/cm by the flat rolls whose surface
temperatures were 140.degree. C. to produce a spunbonded non-woven
fabric in which a fiber diameter of a continuous filament was 10
.mu.m, weight per unit area was 35 g/m.sup.2 and a thickness was
0.15 mm.
[0167] Two sheets of the obtained spunbonded nonwoven fabrics were
superimposed on each other, and the superimposed spunbonded
nonwovens were supported between a pair of upper/lower steel flat
rolls, and after the flat rolls were heated so that a surface
temperature of the upper steel flat roll was 170.degree. C. and a
surface temperature of the lower steel flat roll was 80.degree. C.,
the superimposed spunbonded nonwoven were thermocompression bonded
at a line pressure of 170 kg/cm to produce a spunbonded nonwoven
fabric in which weight per unit area was 70 g/m.sup.2 and a
thickness was 0.10 mm to obtain a support for a separation
membrane. The results are shown in Table 2.
Example 8
[0168] The polyethylene terephthalate resin (a) and the
copolymerization polyester resin (b), which were used in Example 1,
were melted at 295.degree. C. and 280.degree. C., respectively.
These polyethylene terephthalate resin (a) and copolymerization
polyester resin (b) were extruded from a pore as a core component
and a sheath component, respectively, at a nozzle temperature of
300.degree. C. in proportions of the core and the sheath of 80:20
by weight, and these components were spun into concentric filaments
of a core-sheath type having a circular cross section at a spinning
speed of 4500 m/min with an ejector, and the resulting filaments
were collected as a fibrous web on a moving net conveyor. The
collected fibrous web was supported between a pair of upper/lower
steel flat rolls and preliminarily thermocompression bonded at a
line pressure of 40 kg/cm by the flat rolls whose surface
temperatures were 130.degree. C. to produce a spunbonded non-woven
fabric in which a fiber diameter of a continuous filament was 10
weight per unit area was 30 g/m.sup.2 and a thickness was 0.13
mm.
[0169] Further, by changing only a line speed in the
above-mentioned production method, a spunbonded nonwoven fabric, in
which a fiber diameter of a single fiber was 10 .mu.m, weight per
unit area was 40 g/m.sup.2 and a thickness was 0.17 mm, was
produced.
[0170] The spunbonded nonwoven fabric, in which weight per unit
area was 30 g/m.sup.2, of two spunbonded nonwoven fabrics thus
obtained was superimposed on the spunbonded nonwoven fabric in
which weight per unit area was 40 g/m.sup.2, and the superimposed
spunbonded nonwovens were supported between a pair of flat rolls in
which an upper flat roll was made of steel and a lower flat roll
was made of an urethane resin, and after only the upper flat roll
was heated so that its surface temperature was 180.degree. C. and a
surface temperature of the lower resin flat roll was stabilized at
80.degree. C., the superimposed spunbonded nonwovens were
thermocompression bonded at a line pressure of 170 kg/cm to produce
a spunbonded nonwoven fabric in which weight per unit area was 70
g/m.sup.2 and a thickness was 0.10 mm to obtain a support for a
separation membrane. The results are shown in Table 2.
TABLE-US-00002 TABLE 2 Example 5 Example 6 Example 7 Example 8
Resin*.sup.1 PET/co-PET PET/co-PET PET/co-PET PET/co-PET Species of
sheet Spunbonded Spunbonded Spunbonded Spunbonded nonwoven nonwoven
nonwoven nonwoven fabric fabric fabric fabric Spinning speed
(m/min) 4500 4500 4500 4500 Number of layers 1 2 2 2 Bonding method
two step two step two step two step Thermo- Species of roll steel/
steel/ steel/ steel/ compression upper/lower steel resin steel
resin bonding Surface temperature 170/90 170/100 170/80 180/80 roll
upper/lower (.degree. C.) Line pressure 170 170 170 170 (kg/cm)
Fiber diameter (.mu.m) 10 10 10 10 Weight per unit area (g/m.sup.2)
75 70 70 70 Thickness at normal load 0.10 0.10 0.10 0.10 (mm) at
low load 0.11 0.11 0.11 0.11 at high load 0.10 0.10 0.10 0.10
Change rate of thickness (mm) 0.01 0.01 0.01 0.01 Density
(g/cm.sup.3) 0.8 0.7 0.7 0.7 Packed density 0.5 0.5 0.5 0.5 Tensile
Machine 401 397 388 414 strength direction (MD) (N/5 cm) Crosswise
189 203 196 208 direction (CD) Ratio of machine 2.1 2.0 2.0 2.0
direction to crosswise direction Tensile Machine 25 44 38 38
elongation direction (MD) (%) Crosswise 22 41 36 37 direction (CD)
Product of Machine 501 572 535 571 tensile direction (MD) strength
Crosswise 231 286 267 285 and tensile direction (CD) elongation
(N/5 cm) Stress of Machine 232 220 220 226 elongation direction
(MD) of 5% Crosswise 127 120 120 122 (N/5 cm) direction (CD) Ratio
of machine 1.8 1.8 1.8 1.9 direction to crosswise direction
Coefficient of variance of 4.3 3.6 3.7 3.6 luminance of transmitted
light (%) Air permeability (cc/cm.sup.2/sec) 2.4 2.2 2.6 2.4
Surface roughness Ra (.mu.m) 4 4 4 4 Degree of strike through of
cast 4 5 5 5 liquid during film formation (number of points)
Depression Machine direction of 27 29 29 28 rate of nonwoven fabric
separation Crosswise direction 34 35 35 35 membrane of nonwoven
fabric (.mu.m) *.sup.1PET: polyethylene terephthalate, co-PET:
copolymerization polyethylene terephthalate
Example 9
[0171] The polyethylene terephthalate resin (a) used in Example 1
and a polybutylene terephthalate resin (c) containing 10 mole % of
isophthalic acid as a copolymerization component and having a
melting point of 211.degree. C., which was dried to a water content
of 50 ppm or less, were melted at 295.degree. C. and 260.degree.
C., respectively. These polyethylene terephthalate resin (a) and
copolymerization polybutylene terephthalate resin (c) were extruded
from a pore as a core component and a sheath component,
respectively, at a nozzle temperature of 295.degree. C. in
proportions of the core and the sheath of 80:20 by weight, and
these components were spun into concentric filaments of a
core-sheath type having a circular cross section at a spinning
speed of 4500 m/min with an ejector, and the resulting filaments
were collected as a fibrous web on a moving net conveyor. The
collected fibrous web was supported between a pair of upper/lower
steel flat rolls and preliminarily thermocompression bonded at a
line pressure of 50 kg/cm by the flat rolls whose surface
temperatures were 130.degree. C. to produce a spunbonded nonwoven
fabric in which a fiber diameter of a continuous filament was 11
.mu.m, weight per unit area was 30 g/m.sup.2 and a thickness was
0.13 mm.
[0172] Two sheets of the obtained spunbonded nonwoven fabrics were
superimposed on each other, and the superimposed spunbonded
nonwovens were supported between a pair of flat rolls in which an
upper flat roll was made of steel and a lower flat roll was made of
an urethane resin, and after only the upper flat roll was heated to
160.degree. C. and a surface temperature of the resin roll was
stabilized at 90.degree. C., the superimposed spunbonded nonwovens
were further thermocompression bonded at a line pressure of 170
kg/cm to produce a spunbonded nonwoven fabric in which weight per
unit area was 60 g/m.sup.2 and a thickness was 0.09 mm to obtain a
support for a separation membrane. The results are shown in Table
3.
Example 10
[0173] The polyethylene terephthalate resin (a) used in Example 1
was melted at 295.degree. C., and the melted resin (a) was extruded
from a pore at a nozzle temperature of 300.degree. C. and spun into
a continuous filament having a circular cross section at a spinning
speed of 4000 m/min with an ejector, and the resulting filaments
were collected as a fibrous web on a moving net conveyor. The
collected fibrous web was supported between a pair of upper/lower
steel flat rolls and thermocompression bonded at a line pressure of
70 kg/cm by the flat rolls whose surface temperatures were
230.degree. C. to produce a spunbonded nonwoven fabric in which a
fiber diameter of a continuous filament was 14 .mu.m, weight per
unit area was 90 g/m.sup.2 and a thickness was 0.15 mm to obtain a
support for a separation membrane. The results are shown in Table
3.
Example 11
[0174] The polyethylene terephthalate resin (a) used in Example 1
was extruded from a pore at a nozzle temperature of 300.degree. C.
and spun into a continuous filament having a circular cross section
at a spinning speed of 4500 m/min with an ejector, and the
resulting filaments were collected as a fibrous web on a moving net
conveyor. The collected fibrous web was supported between a pair of
upper/lower steel flat rolls and thermocompression bonded at a line
pressure of 60 kg/cm by the flat rolls whose surface temperatures
were 230.degree. C. to produce a spunbonded nonwoven fabric in
which a fiber diameter of a continuous filament was 12 .mu.m,
weight per unit area was 60 g/m.sup.2 and a thickness was 0.09 mm
to obtain a support for a separation membrane. The results are
shown in Table 3.
Example 12
[0175] A poly(L-lactic acid) resin (d) having a weight average
molecular weight of 150000, a Q value (Mw/Mn) of 1.51 and a melting
point of 168.degree. C. was melted at 230.degree. C., and the
melted resin (d) was extruded from a pore at a nozzle temperature
of 235.degree. C. and spun into a continuous filament having a
circular cross section at a spinning speed of 4300 m/min with an
ejector, and the resulting filaments were collected as a fibrous
web on a moving net conveyor. The collected fibrous web was
supported between a pair of upper/lower steel flat rolls and
thermocompression bonded at a line pressure of 60 kg/cm by the flat
rolls whose surface temperatures were 150.degree. C. to produce a
spunbonded nonwoven fabric in which a fiber diameter of a
continuous filament was 11 .mu.m, weight per unit area was 90
g/m.sup.2 and a thickness was 0.12 mm to obtain a support for a
separation membrane. The results are shown in Table 3.
TABLE-US-00003 TABLE 3 Example 9 Example 10 Example 11 Example 12
Resin*.sup.1 PET/co-PBT PET PET PLA Species of sheet Spunbonded
Spunbonded Spunbonded Spunbonded nonwoven nonwoven nonwoven
nonwoven fabric fabric fabric fabric Spinning speed (m/min) 4500
4000 4500 4300 Number of layers 2 1 1 1 Bonding method two step one
step one step one step Thermo- Species of roll steel/ steel/ steel/
steel/ compression upper/lower resin steel steel steel bonding
Surface temperature 160/90 230/230 230/230 150/150 roll upper/lower
(.degree. C.) Line pressure 170 70 60 60 (kg/cm) Fiber diameter
(.mu.m) 11 14 12 11 Weight per unit area (g/m.sup.2) 60 90 60 90
Thickness at normal load 0.09 0.15 0.09 0.12 (mm) at low load 0.10
0.16 0.10 0.13 at high load 0.09 0.14 0.09 0.12 Change rate of
thickness (mm) 0.01 0.02 0.01 0.01 Density (g/cm.sup.3) 0.7 0.6 0.7
0.8 Packed density 0.5 0.4 0.5 0.6 Tensile Machine 280 521 290 243
strength direction (MD) (N/5 cm) Crosswise 126 171 102 91 direction
(CD) Ratio of machine 2.2 3.0 2.8 2.7 direction to crosswise
direction Tensile Machine 35 27 24 12 elongation direction (MD) (%)
Crosswise 32 25 23 7 direction (CD) Product of Machine 378 662 360
272 tensile direction (MD) strength Crosswise 166 214 125 97 and
tensile direction (CD) elongation (N/5 cm) Stress of Machine 170
270 151 220 elongation direction (MD) of 5% Crosswise 90 120 64 85
(N/5 cm) direction (CD) Ratio of machine 1.9 2.3 2.4 2.6 direction
to crosswise direction Coefficient of variance of 3.9 5.0 4.8 4.6
luminance of transmitted light (%) Air permeability
(cc/cm.sup.2/sec) 6.8 5.2 7.5 4.2 Surface roughness Ra (.mu.m) 4 5
4 4 Degree of strike through of cast 5 4 4 4 liquid during film
formation (number of points) Depression Machine direction of 33 24
34 29 rate of nonwoven fabric separation Crosswise direction 37 35
46 38 membrane of nonwoven fabric (.mu.m) *.sup.1PET: polyethylene
terephthalate, co-PET: copolymerization polyethylene terephthalate
Co-PBT: copolymerization polybutylene terephthalate, PLA:
poly(lactic acid)
Example 13
[0176] The poly(L-lactic acid) resin (d) used in Example 12 was
melted at 230.degree. C., and the melted resin (d) was extruded
from a pore at a nozzle temperature of 235.degree. C. and spun into
a continuous filament having a circular cross section at a spinning
speed of 4300 m/min with an ejector, and the resulting filaments
were collected as a fibrous web on a moving net conveyor. The
collected fibrous web was supported between a pair of upper/lower
steel flat rolls and preliminarily thermocompression bonded at a
line pressure of 30 kg/cm by the flat rolls whose surface
temperatures were 110.degree. C. to produce a spunbonded nonwoven
fabric in which a fiber diameter of a continuous filament was 11
.mu.m, weight per unit area was 40 g/m.sup.2 and a thickness was
0.16 mm.
[0177] Two sheets of the obtained spunbonded nonwoven fabrics were
superimposed on each other, and the superimposed spunbonded
nonwovens were supported between a pair of flat rolls in which an
upper flat roll was made of steel and a lower flat roll was made of
resin, and after only the upper flat roll was heated to 150.degree.
C. and a surface temperature of the resin flat roll was stabilized
at 60.degree. C., the superimposed spunbonded nonwovens were
further thermocompression bonded at a line pressure of 150 kg/cm to
produce a spunbonded nonwoven fabric in which weight per unit area
was 80 g/m.sup.2 and a thickness was 0.11 mm to obtain a support
for a separation membrane. The results are shown in Table 4.
Example 14
[0178] The polyethylene terephthalate resin (a) and the
copolymerization polyester resin (b), which were used in Example 1,
were melted at 295.degree. C. and 280.degree. C., respectively.
These polyethylene terephthalate resin (a) and copolymerization
polyester resin (b) were extruded from a pore as a core component
and a sheath component, respectively, at a nozzle temperature of
300.degree. C. in proportions of the core and the sheath of 80:20
by weight, and these components were spun into concentric filaments
of a core-sheath type having a circular cross section at a spinning
speed of 4500 m/min with an ejector, and the resulting filaments
were collected as a fibrous web on a moving net conveyor. The
collected fibrous web was supported between a pair of upper/lower
steel flat rolls and preliminarily thermocompression bonded at a
line pressure of 40 kg/cm by the flat rolls whose surface
temperatures were 140.degree. C. to produce a spunbonded non-woven
fabric in which a fiber diameter of a continuous filament was 11
.mu.m, weight per unit area was 20 g/m.sup.2 and a thickness was
0.10 mm.
[0179] Five sheets of the obtained spunbonded nonwoven fabrics were
superimposed on one another, and the superimposed spunbonded
nonwovens were supported between a pair of flat rolls in which an
upper flat roll was made of steel and a lower flat roll was made of
resin, and after the upper steel flat roll was heated so that its
surface temperature was 170.degree. C. and a surface temperature of
the resin flat roll was stabilized at 50.degree. C., the
superimposed spunbonded nonwovens were further thermocompression
bonded at a line pressure of 180 kg/cm to produce a spunbonded
nonwoven fabric in which weight per unit area was 100 g/m.sup.2 and
a thickness was 0.13 mm to obtain a support for a separation
membrane. The results are shown in Table 4.
Example 15
[0180] The polyethylene terephthalate resin (a) and the
copolymerization polyester resin (b), which were used in Example 1,
were melted at 295.degree. C. and 280.degree. C., respectively.
These polyethylene terephthalate resin (a) and copolymerization
polyester resin (b) were extruded from a pore as a core component
and a sheath component, respectively, at a nozzle temperature of
300.degree. C. in proportions of the core and the sheath of 80:20
by weight, and these components were spun into concentric filaments
of a core-sheath type having a circular cross section at a spinning
speed of 4500 m/min with an ejector, and the resulting filaments
were collected as a fibrous web A on a moving net conveyor. The
collected fibrous web A was carried with a net conveyor, and
spinning was carried out in the same procedure as in the fibrous
web A and filaments were collected as a fibrous web B on a moving
fibrous web A. The collected fibrous web consisting of two layers A
and B was supported between a pair of upper/lower steel flat rolls
and thermocompression bonded at a line pressure of 60 kg/cm by the
flat rolls whose surface temperatures were 190.degree. C. to
produce a spunbonded nonwoven fabric in which a fiber diameter of a
continuous filament was 11 .mu.m, weight per unit area was 80
g/m.sup.2 and a thickness was 0.11 mm to obtain a support for a
separation membrane. The results are shown in Table 4.
Comparative Example 1
[0181] A stretched polyethylene terephthalate short fiber having a
fiber diameter of 10 .mu.m and a length of 10 mm, a stretched
polyethylene terephthalate short fiber having a fiber diameter of
13 .mu.m and a length of 10 mm and a nonstretched polyethylene
terephthalate short fiber having a fiber diameter of 11 .mu.m and a
length of 5 mm were mixed in water in proportions of 20:40:40 by
weight, and then adequately dispersed to prepare aqueous slurry
having a fiber concentration of 0.05%. The slurry was sent to a
circular net paper machine, paper made and dried by a Yankee drier
of 120.degree. C. and taken up to produce a paper made web. The
obtained paper made web was supported between a pair of flat rolls
in which an upper flat roll was made of steel and a lower flat roll
was made of an cotton, and after only the upper flat roll was
heated so that its surface temperature was 150.degree. C. and a
cotton flat roll was stabilized at 80.degree. C., the spunbonded
nonwovens was further thermocompression bonded at a line pressure
of 150 kg/cm to produce a paper made nonwoven fabric in which
weight per unit area was 80 g/m.sup.2 and a thickness was 0.11 mm
to obtain a support for a separation membrane. The results are
shown in Table 4.
TABLE-US-00004 TABLE 4 Comparative Example 13 Example 14 Example 15
Example 1 Resin*.sup.1 PLA PET/co-PET PET/co-PET PET Species of
sheet Spunbonded Spunbonded Spunbonded Paper made nonwoven nonwoven
nonwoven nonwoven fabric fabric fabric fabric Spinning speed
(m/min) 4300 4500 4300 -- Number of layers 2 5 2 1 Bonding method
two step two step one step one step Thermo- Species of roll steel/
steel/ steel/ steel/ compression upper/lower resin resin steel
cotton bonding Surface temperature 150/60 170/50 190/190 150/80
roll upper/lower (.degree. C.) Line pressure 150 180 60 150 (kg/cm)
Fiber diameter (.mu.m) 11 11 11 10/13 Weight per unit area
(g/m.sup.2) 80 100 80 80 Thickness at normal load 0.11 0.13 0.11
0.11 (mm) at low load 0.12 0.14 0.12 0.12 at high load 0.11 0.13
0.11 0.11 Change rate of thickness (mm) 0.01 0.01 0.01 0.01 Density
(g/cm.sup.3) 0.7 0.8 0.7 0.7 Packed density 0.6 0.6 0.5 0.5 Tensile
Machine 215 598 421 393 strength direction (MD) (N/5 cm) Crosswise
88 242 169 69 direction (CD) Ratio of machine 2.4 2.5 2.5 5.7
direction to crosswise direction Tensile Machine 14 39 25 15
elongation direction (MD) (%) Crosswise 10 35 17 16 direction (CD)
Product of Machine 245 831 526 452 tensile direction (MD) strength
Crosswise 97 327 198 80 and tensile direction (CD) elongation (N/5
cm) Stress of Machine 200 261 271 180 elongation direction (MD) of
5% Crosswise 70 142 130 40 (N/5 cm) direction (CD) Ratio of machine
2.9 1.8 2.1 4.5 direction to crosswise direction Coefficient of
variance of 3.8 2.2 4.4 3.8 luminance of transmitted light (%) Air
permeability (cc/cm.sup.2/sec) 4.4 1.1 1.9 1.2 Surface roughness Ra
(.mu.m) 4 3 4 4 Degree of strike through of cast 5 5 4 4 liquid
during film formation (number of points) Depression Machine
direction of 30 24 24 32 rate of nonwoven fabric separation
Crosswise direction 42 33 34 53 membrane of nonwoven fabric (.mu.m)
*.sup.1PET: polyethylene terephthalatec, co-PET: copolymerization
polyethylene terephthalate PLA: poly(lactic acid)
[0182] Characteristics of the support for a separation membrane
obtained are shown in Tables 1 to 4.
[0183] Each of the supports for a separation membrane obtained in
Examples 1 to 15 was fixed to the surface of a glass plate, and
thereon, 15% by weight dimethylformamide solution (cast liquid) of
polysulfone ("Udel"(registered trade mark)-P3500 manufactured by
SOLVAY Advanced Polymers Co., Ltd.) was casted in a thickness of 50
.mu.m at room temperature (20.degree. C.), and immediately the
glass plate was dipped into pure water at room temperature
(20.degree. C.) and left standing for 5 minutes to form a
separation membrane made of polysulfone.
[0184] In the separation membranes using the supports for a
separation membrane in Examples 1 to 15, a degree of strike through
of a cast liquid during film formation was score 4 or more.
Further, peeling, a nonuniform membrane and a pinhole defect are
not present in any membrane and film-forming properties were good.
Further, all the separation membranes using the supports for a
separation membrane in Examples 1 to 15 were superior in durability
since all depression rate of a separation membrane was 50 .mu.m or
less.
[0185] On the other hand, a separation membrane made of polysulfone
was also formed for the support for a separation membrane obtained
in Comparative Example 1 as with the supports for a separation
membrane obtained in Examples 1 to 15. In the separation membrane
using the support for a separation membrane in Comparative Example
1, a degree of strike through of a cast liquid during film
formation was score 4 or more, but there were membrane defects that
fibers of the support for a separation membrane protrude beyond the
separation membrane surface. Further, the support for a separation
membrane in Comparative Example 1 was inferior in durability since
the depression rate of a separation membrane in a lateral direction
of the nonwoven fabric was as large as 53 .mu.m.
* * * * *